Sony TC RX70ES Cassette Deck Repair (Belt Swap, Lube)

Sony ES Cassette Deck

No great pics of the deck during this post, maybe I will update.

So I swung by a Goodwill to donate some things, and did a quick check. I never find vintage computers, and most of the video games are picked over. I never find that copy of Space Quest III. But on this trip I did find a Sony TC RC70ES. I debated with myself over it for a little while. It didn’t have the wood ends, so it doesn’t really seem like a ES home component. But it is an ES deck. Less than a year ago I picked up the Nak 680 and have been enjoying it, so why not a little competition? And I tried to fix my childhood Sony dual tape deck and failed — so that still stung a bit. Should I? Yeeeaaa why not.

Brought it home right as I went on vacation. Diving in Jupiter with Eric, Chris and Mary! Chilling in Key West. South Beach Miami! Silverball Museum in Del Ray! Hanging with family. And pre-ordering some belts for this thing from eBay.

So when I got home from vacation the parts were there and ready to swap.

First, the old belt was nasty AF. It was goo, and the goo got on everything. Rubbing alcohol cleaned it off well, but I have no idea if that will hurt the new belts.

Removing the first layer to get to the flywheels was no problem. But the next layer of disassembly resulted in parts popping out all over. So service manual was found, so that is good. People care enough about this model for it to be out there.

Got it back together, annnnnd BAM. Sounded bad. I had to play with the speed adjustment on the motor, but I don’t have a real reference tape. I recorded 400hz from youtube on the Nak (which is not speed calibrated) and threw it in the Sony. It seemed to be moving all over the place.

But the Nakamichi didn’t just work. It seemed to come to life after playing a tape or two and loosening up. So I ran a tape on the ES.

After one side it started squealing. LOUDLY. I ran. I ran so far away. Hit power button. Did some quick google research, and as I remembered the pointer is to the drive motor that moves the capstans. So I put a drop or two of oil on it via a syringe type device used for purging air from printer lines. It cleared up pretty quickly. But not sure if mineral oil is ideal.

The speed still seems to be unreliable, and I don’t know that I really like the sound quality. The CrO2 tape that I recorded Capital Cities – A Tidal Wave of Mystery on the Nak when played back on the Sony just isn’t the same. First the deck detects the CrO2 and you loose high end I think. And there is more hiss. So far I don’t have much of a love relationship with the deck, but I still like the Nak 680 a lot.

Also, after working on the Sony ES deck I now know that I could have probably fixed that childhood Sony deck with motor lubrication. The mechanisms are still crazy complex, kudos to the Sony engineers that came up with auto reverse system and rotating head and all of that.

Time will tell on this deck. Next will be to get a real calibration tape. But I fear I might have to rebuild the motor as well, and I’m not sure of my motivation on it.

Digital Music Corp MX-8 MIDI Patchbay power supply repair

Digital Music Corp MX-8 repair

Years ago I picked up a handy unit called the MX-8. I think I found it for $20 on craigslist. The unit has 8 or so inputs and 8 or so outputs. You can software connect any input to any output. It can do data inspection and changes and other stuff, but all I use it for is basically a multi thru box.

I tend to leave my cheapest synthesizer on all the time, it’s a Roland JV-30. I bought that dead, swapped a diode on the power input and it was good to go. By leaving the keyboard, MX-8 and one MIDI module on all the time I am more tempted to stop and bang around on the keyboard a little.

All this uptime on the little MX-8 eventually resulted in it dying. Hit keyboard key, nothing happened. Figured power loss wiped out the current settings but nope, no power.

First I checked the fuse, but the fuse broke off in the fuse holder and wouldn’t come out. Fuses blow for a reason anyways.

De-racked unit and popped lid off. Was always curious what was inside.

CR-2032 (I think that is the size) lithium battery holds the memory. If your MX-8 forgets everything, this battery is easy to replace and this should fix your issue.

The power issue was a standard ?7805? voltage regulator. It died from heat. The heat is from being left on 24×7 for 10 years. When I replaced it, I re-spooged it with some fake artic silver heatsink compound. For sport, I added a 2nd heatsink behind the factory one so there is a bit more surface area ti dissipate heat.

Unit looks well made inside.

I think the hardest part of this entire ordeal was replacing the fuse holder I broke.

I did consider moving to a switch mode power supply, like from a phone charger. I didn’t have anything handy so I just kept it on the original linear regulator. I could save some heat and power by converting it. Perhaps next time.

Sony PVM-2030 (Thanks Matt!) Tune Up

One of my… Let me re-phrase this. My favorite TV design of all time is the Sony PVM “cube” monitor. It’s an early 80s television set where the back of the TV is framed in with a plastic and perhaps metal frame that makes the TV perfectly square. On the left and right of the screen there are touch buttons. The text of the buttons is invisible until you press one button that turns on illumination behind these. It’s just so damn cool, and it’s from the early 80s.

I owned one before, a 25″ or 27″ model. But the picture wouldn’t always come on and I didn’t know why. At that point in my life I was still under the idea that I would never, ever, repair televisions. High voltage risk and all that. My attitude changed when I got my 2nd arcade cabinet and it had a failing Wells Gardner open frame monitor in it. But my early 25″ or 27″ PVM monitor would snap and the picture would go away. Or it wouldn’t come up at all. I now know the issue is probably the take off feed on the anode line from the flyback. But I sold that old monitor many years ago.

So it has been kind of a thing to want to pick up one of the smaller 20″ versions of my favorite TV. I’m not a super CRT enthusiast, I keep a few around for old computers. I keep my arcades on CRTs. But I don’t consider myself a die hard.

Opportunity hit and my good friend Matt had a PVM-2030 that was said to not work. And I could have it. Thanks Matt! So he brought it to me on one of his trips up to my area. I finally got around to checking it out. It just seemed to work. No repairs needed! It has some rash, some rough scrapes on one side. But who looks at the side.

I hooked it up to what I had laying around. I was too lazy to hook it up to the sencore signal generator that I usually use to poke at arcade monitors. But I found an old Video Essentials DVD and threw it in an XBox Classic. Things were looking okay! Until I noticed that the picture was kind of crooked. And maybe some convergence issues.

Off came the cover!

First thing I did was to hunt for the schematics. I couldn’t find them. I did find the PVM-2530 schematics, and low and behold there is an adjustment that will rotate the screen. Except the PCB it is on in the PVM-2530 model doesn’t exist in the PVM-2030. Most likely old caps have caused it to drift. So my fix, with a ton of sweat was to rotate the yoke on the neck of the CRT. Rubber mallet and stick, true sweat.

There are some adjustments found through holes on the sides. I used plastic CRT adjustment tools that can be found from electronics parts places. Blue plastic thing with rainbow of tools. The tools are poor quality, and I was disappointed when I tried to use them to adjust arcade monitors (mainly the hex width coil on G07.) But they came in handy with the Sony.

I don’t have the speakers for the TV, they were an option and mount to the sides. They come up on feeBay from time to time for around $50. I might pick a set up some day. I will only go for the “APM” flat and square speakers since those were the ones I remember.

I haven’t built any fun cables for the RGB input. IIRC I could probably feed the output from an arcade PCB to this TV, or maybe an Amiga.

I sharpened the picture up a bit and tried my best with the convergence playing with the rings on the back of the neck. That too took a good amount of time. There is still convergence drift on a test pattern in some of the corners as I recall.

Overall though, mission accomplished! Still an awesome physical design. I think PVMs became way more advanced and my choice of one from that point lead to a TV that does not have as good of a picture that later (and especially the Broadcast series BVM) but whatever. Also, those sexy pushbuttons for adjustments? Without onscreen displays and without some indication that you are in the middle it is impossible to tell what the settings are. If you touch the balance adjustment on the set for the audio there is no way to “center” it again without hitting the reset button, and that reset button will reset all picture tweaks. So that aspect of the TV really falls short.

I do hope the schematics for the set become public at some point. That would be helpful.

Sony PVM-2030 tune up

AMX Netlinx NI-4100 Bad Serial Cap Replacement

10uF cap replacing SMD

This one is pretty well documented on the internet, at least on other AMX platforms. AMX is my automation platform of choice, because it’s so damn flexible. You can write anything in the Netlinx language for the most part, and it’s easy to talk to external things be it via tcp or RS-232/485/422.

There is an issue with the NI-3000/2000 series where the serial ports can no longer transmit due to a bad cap. In my case my NI-4100 didn’t seem to have working serial ports, so I reverted to using the NXC-COM2 boards that were in the unit that added an addition 8 serial ports on top of the on board 7.

After struggling a lot with strange issues using the NXC-COM2 ports, I said screw it let’s replace this capacitor. I wasn’t enthusiastic to remove the unit from the rack but really the job went very quickly.

The cap is a simple 35v 10uF IIRC, and it’s originally a SMD cap but way easy to replace with a through hole with bent legs. Look at that pic, it looks nice! Especially compared to dealing with Konami XMen PCB where the caps leaked all over the board and ate the traces.

The board inside the unit is probably the same board used in the NI-3000, just with the additional board at the bottom for adding the expansion boards. If anything, I plan to “downgrade” to a NI-3000 as I like the form factor a bit better, but in the meantime the DB-9 serial port is running strong (still had issues with the NXC-COM2 after cap replacement, I think it’s my wiring.)

So this worked well.

On that note, I will post some stuff I hacked together for grabbing weather from wunderground and getting into the AMX system for pushing weather forecast data to the AMX EnvStat communicating color thermostat. Mine jams up a bit, it’s been frustrating since it falls out of hold modes based on the schedule (I said hold damnit!) But got the weather hitting the stat via a Linux host, and able to poll thermostat from IRC (No clouds in this forecast.)

BK Precision 1672 Power Supply – Dead channel repair

BK Precision Power Supply test, after chip replacement

Some friends were crashing at my place after MAGFest for the local Awesome Games Done Quick (AGDQ) event. At the time I had a lamp in one of the spare bedrooms but the 2nd spare bedroom had no light source. There is a switched outlet tied to a light switch, but I couldn’t think of any lamp fixtures sitting around that aren’t coherent light or require a DMX-512 protocol. Womp womp, just remembered one in the garage come to think of it. Any how, as a quick fix to solve the issue what better thing to use for a lamp than a 15′ strip of LEDs and a bench power supply? Both were handy, so I grabbed them and cobbled together a 1 minute solution to solve the temporary problem. All is good, except the strip curled back up on itself and shorted. The power supply, a nice BK Precision 1672 with current limiting went into protect mode, but something strange happened. The channel was killed.

Upon investigation the unit would always be stuck in constant current (CC) mode and there was no output. My first suspect was easy, the TO3 transistor might be shorted. No, not it. There were 4 or 5 fuses on each of the power supply boards inside, all were fine. I shot off an email to their support. They kindly replied fairly quickly saying they couldn’t help – but here is the schematics. How is that for service? So awesome.

Looking at the schematics and halfway guessing, I notice a lot of 741 opamps. They are all socketed, so the first easy thing to try is just replace them all. Cheap component, easy work (sort of.) My co-worker Will was placing a Mouser order and offered to let me jump in on it, so some replacement DIP 741’s were had.

Removing the PCB was actually a pretty huge pain. The way the unit is put together, it’s pretty tough to service (although with the bottom of the PCB exposed, I bet shops highly familiar can make easy work of taking measurements.) After freeing the board which requires moving the front knobs, the pot retaining nuts, 4 screws that hold the board in, the metal bracket above the board, and loosening the front plastic and disconnecting a bunch of cables that have little slack I was able to quickly and easily replace all op-amps.

Upon first test it didn’t seem to work right., the voltage adjustment worked like a champ but the current adjustment didn’t — no output. I wanted to keep the unit all together, and figured I’ll just use the right channel and +5vdc.

Upon putting it all back together, I tested it again and it worked fine. I’m thinking one of the connectors wasn’t seated fully, at least that is what I’m telling myself. So the lovely power supply is back in action 100%, thanks for the schematics BK and thanks Will for the 741’s!

And yea, I got a simple lamp for the room.

C64 Audio Issues

C64 No Audio

Picked up a totally sweet SD2IEC board which allows emulation of the Commodore floppy drive from a SD card. It’s similar to the SIO2SD boards that do a similar function for the Atari family of home computers, except for C64. After getting it hooked up and being fairly impressed with the unit I noticed that my C64 doesn’t have sound. The one thing the machine is known for — it’s missing.

First step was checking power supplies. Oddly I had a 2nd PSU on hand, swapped it in place and no go. The internet said it could be a culprit, this makes sense as the power supply has a DC line which would be used by the logic chips that make up the computer as well as an AC line which is commonly used for opamp ICs and stuff that has a +/- power feed. Anyhow the power supply checked out A-OK which doesn’t solve issue.

Next step was to open the thing up, and hunt. Looking online I found details where the SID chip was and the datasheet. Poking at the chip while a music disk / demo was playing I could see the address and data lines were busy so not decode logic or data bus buffers to the naked eye. The thing is the output side of the chip just sits at a high voltage so it seems toasted. I didn’t check the two external capacitors, maybe later. The thing is the SID chip is the value of the machine and places like eBay are full of fake copies from China that don’t function. So this one goes on the shelf until a parts machine turns up.

UPDATE 5/3/2917

Matt Crainer brought me a donor C64 that had already been robbed of it’s keyboard controller IC. I carefully de-soldered the SID chip. I didn’t have a 28 pin DIP socket on hand, and instead of ordering one I ordered some break-away SIP sockets. The quality of the machine pin holes was not up to that of what I would get from a mainstream commercial mail order house machined DIP sockets, but it was good enough. Soldered two 14 position sip sockets. I cleaned up the SID chip first, trying to remove any excess solder or burs on the pins, didn’t want them to bend on insertion. Threw it in. Powered on the C64. I googled for some hints as to how to get sound without digging out the SD drive emulator and found a post from VCF/MARCH forum I believe on some addresses to poke. Noise was heard! All is good. Buttoned it all up and this project is checked off!!!!

Picture added to slides above of soldered in SIP socket.

SGI Indigo R4K Failure – Let out the magic smoke! Burning smell

SGI Indigo Failure

So I *finally* managed to find the keyboard cable for my SGI Indigo on my last trip to Norfolk, VA. This completed what I needed: the 13w3 to VGA cable, the special keyboard and mouse, the system and the keyboard interconnect cable. I humped the thing onto my desk after clearing a bit of space, hooked it up to my monitor, then switched my first SGI on. It powered on! But then came this nasty smell. That’s not good! It did show the clock TOD error, no chime sound (just clicks.)

I originally bought the Indigo from Reputable Systems (Greg Douglas) in the 90s. I was working tech support at the time, living with my parents, and it cost a good chunk of cash — especially by todays standards. Originally it was R3K with a lower level graphics subsystem that I believe could do some hardware 3d acceleration but only 256 colors. I’ll admit when I first started messing with it I was a bit disappointed. It was still sort of slow, but had good audio capabilities and worked well as an X-term. It wasn’t long before MP3 was a new thing and the system couldn’t decode a 128kbps MP3 real time though, it took about 6 minutes for a 4 minute song — so I would have to write it out then write it to minidisc. Creative commons licensed music, of course.

Somewhere along the lines in my SGI fandom I think I ended up with a 9u VME frame that had an ELAN graphics boardset on it. I also ended up with a 2nd SGI Indigo from NASA auctions I used to frequent, one with the faster MIPS R4000 series CPU (R4K.) I remember posting that I was giving away a bunch of hardware including parts from the NASA Indigo, and left it and other stuff behind my office in Virginia Beach for someone else to pick up. But a homeless scrapper got to it first, taking everything metal and leaving plastic shards of laser printers and SGI Indigo (and other equipment) behind. Ugh.

But I held onto my Indigo, not having looked at the CPU cards in a long time. The first thing I did was pull out the CPU card and thought, “man this is bulkier than I remember! What a crazy heatsink for this slow R3000 processor.” But it turns out the R3K board isn’t a R3K board, it’s a R4K board. So then I’m thinking, “Okay so I guess I kept the R4K CPU and the lower graphics board.” But no, the graphics boardset looks stout. So I guess I kept both higher end parts and gave away the old R3K / Entry stuff. Or maybe the Entry graphics was in one of the bigger deskside systems on the frame the Elan came on. I can’t remember.

I remember that the Indigo had two power supply options. One for R3K/Elan graphics and one for R4K. I thought you could use a R4K with entry graphics on the weaker power supply as well. This was a huge issue in my mind since I figured my Indigo had the R3K PSU. I pulled the PSU from Indigo (My Indigo was always named Eggbert from a Super Mario Bros 2 character of similar name that was purple, so from here on it’s Eggbert.) So Eggbert’s PSU turns out to be the R4K model! I opened it up, the capacitors look okay but that really doesn’t say much. No burnt smell inside PSU.

So back to sniffing the circuit boards more. I sniffed and sniffed. Two times over I missed the roasted capacitor on the bottom of the CPU card. I was thinking it had come from the graphics boardset, which sits in the case right next to the bottom of the CPU boardset.

The fried capacitor is C531, and this is near the sound section of the CPU board. No telling what it actually goes to but the lack of the chime sound might have something to do with it. Image slideshow above has a picture of the fried capacitor. Audio sections of computers often use the negative voltages for opamps and DACs where the rest of the computer might not use these voltages, so I might have to check to make sure the power supply isn’t doing something bad on the negative voltage outputs (if it has them.)

In the process of diagnosis I have made a list of all similar style capacitors on the board. I don’t know what is wrong with the machine, but if this style/make of capacitor is degrading from age then the solution should be to replace them. They’re SMD, but pretty large SMD so replacement shouldn’t be TOO bad.

So here is a list of the capacitors I have made so far. I’ve only researched 2 of the 4 with regards to what standard the size is. I have what I believe are DigiKey part numbers for the value that fried and the most common other value (prob used for noise filtering on the power rail.)

I measured the size with a caliper and best guessed on what it equates to in industry.


SGI Indigo SMD tantalum caps of the style of the one that burned up:

Top of PCB:
C14, C15, C23, C48 = 47uF,16v
C30 = 33uF, 20v

Bottom of PCB:
C555, C544, C525, C513A, C513B, C578A, C578B, C645A, C645B = 47uF, 16V
C697 = 33uF, 16v
C551 = 33uF, 20V
C507? = 10uF, 10V

C551 is the crispy one

47uF/16v = 7.3mm x 4.42mm : Size 2917 (7343 Metric) / Digikey – 478-1739-1-ND
33uF/20v = 7.44mm x 4.33mm : Size 2917 (7343 Metric) / Digikey – 399-3788-1-ND
10uF/10v = 5.5mm x 3.3mm :
33uF/16v = 7mm x 4.45mm :


I will also have to do a battery holder mod since TOD battery is dead.

More updates once replacement caps come in and I replace them.

GeForce FX5200 overhaul, Andamiro Mark 6.1 / VI – Pump It Up Arcade Hardware – Fan, Swollen Capacitors

Andamiro Mark VI / GeForce FX5200 overhaul

A few years ago I got a decent deal on a dead Pump It Up NX2 cabinet (Thanks Matt!) I was originally after a DDR machine, settled on a Pump It Up machine, then got a DDR machine while waiting for the PIU deal to go through. Both machines were dead, and needed to be repaired. I suppose they’re always in a state of repair, but that’s okay.

A few weeks ago I let my friend Greg borrow the computer from my Pump It Up machine to do some software development/QA on newer versions of the software that run on these machines (he does contract work for the company that makes it.) While the computer was out of the cabinet, I figured I would replace the cooling fan on the video card. It had seized up before I got the machine. It still runs but it’s probably only a matter of time before disaster hits in the form of DRAM failure or GPU failure.

So while the computer is out I ordered a replacement fan from China for the NVidia card:
Triangle Screw Distance: approx. 25mm between each two
Mounting Hole Dia: approx. 2mm
Dimensions(mm): approx. 36 mm(Diameter)

(See slideshow pics above for pics of the video card.)

These haven’t arrived yet so I don’t know how they will mount up. The fan on my heatsink is removable via 3 small screws access through the blades.

While the card is laying on my desk, I look at it and notice bulging capacitors. Common issue on a lot of electronics, not surprised. To be fair it might be from the excess heat from the GPU not having a running fan, but while we’re rebuilding this thing might as well do it up right!

Caliper measurements on the caps says they’re 8mm x 12mm, 1000uF 6.3V

A good replacement seems to be Digikey Part: P5509-ND Panasonic 105c with 3.5mm lead spacing, 8mm diameter vs 12.5mm height .

Going to add this to my DigiKey order, will update this post with results.

I had to replace the power supply in this computer already. For those that don’t know, EVERYTHING IN THESE PUMP IT UP CABINETS RUN AT 220V. Yes, it’s fed 110-120V but they run a 1:2 ISO transformer!!! Fair warning, if the PSU isn’t auto switch on the computer set it to 220/240v!

And no, I’m not very good at Pump It Up or DDR

QSC RAVE 88s Firmware Update failed, unit bricked (full recovery)

QSC RAVE Firmware Corruption via Update Failure

A while ago I picked up a pair of QSC RAVE 88S. These magic wonders from my favorite commercial audio company use technology from PEAK Audio/Cirrus Logic to shove audio across computer networks at low latency. This system is called CobraNet, and it’s implemented in hardware from a number of companies. I think it’s legacy now, with the newer Dante standard getting all the love. These RAVE 88S are pretty crusty, having been superseded by units from the QSC BASIS line. However, home user + budget = the cheap $20 units from eBay. I remember getting them working, then I put them on a shelf for later use. The 88S models each features 4 stereo pairs of digital audio in and out (AES/EBU, which is like the coaxial connection you find on some CD, DVD, DAT, MiniDisc and computer sound cards. 2 channels, not 5.1 or 7.1. It cannot do 8 channels from ADAT. AES/EBU is the professional version of the digital RCA jack, using a balanced XLR connector.) There are other models that are 16 in, or 16 out, and another series of analog in and out. I’d really like some of the analog ones like the 161S, but there is more competition to get hold of those.

MAGFest is coming up and this is motivation to get a lot of stuff working. I borrowed from my friend Robert 3 CobraNet endpoints from PRN. I didn’t have much luck with them but didn’t realize one of my RAVE 88S wasn’t transmitting any audio on the network so I need to go back and investigate further. The PRN units might attenuate the audio level based on room sound level — not sure. It’s in the patent.

Through the magic of looking at eBay, which I try to avoid, I picked up 3 QSC BASIS 904zz units. These are CobraNet endpoints, they’re much newer, and they have the functionality of controlling the amplifiers I own from QSC. I have an older unit called a CM16A which has similar functionality, but without CobraNet and without the DSP. I didn’t know what I was getting into, but the BASIS is just totally bad ass. Similar to modern DAW programs you can draw out “cable routing” between the CobraNet audio coming in, the DSP system and the amplifiers attached to the unit. Many band EQs, Crossovers, Delays based on feet per second of sound travel… doodle it in the software, sync it to the unit and it’s there. I didn’t even know it could do this stuff, I was just after CobraNet out that worked!

BUT… on to screwing up the firmware in my RAVE units. I was having tons of problems with the PAM units receiving audio from my RAVE units. The RAVE units are configured with this utility known as CobraNet Disco (CobraNet Discovery.) All the CobraNet stuff seems to be based off of reference designs, but I’m not sure 100%. After a lot of fighting with the RAVE boxes I finally decide that I should bring the RAVE units to the same version of CobraNet / firmware as the BASIS units are running and the PRN units are running. So I use the Disco utility + firmware snatched via (RAVE boxes are old!) and … clicked update.

The utility kicks in, does it’s thing till about 3/4ths of the way … then freezes. It says it can’t do it’s thing any more, and halts. I try again, no go. I try to upload the firmware that was in the unit originally, and it doesn’t work either. Take a deep breath, power cycle the thing…. and it’s a 1u rackmount brick.

I try setting the rotary encoders on the front to FFFF, no go. Apparently there is a recovery method outside the one I came up with, TFTP + RARP style that QSC has. But I don’t know the details.

I took my unit apart, because who doesn’t want to know whats inside. It’s a lot of screws. But once inside I notice after picking off a sticker that the main program store chip is an AMD flash device. I pull the chip, throw it in the programmer and save off the contents. For giggles, I upload the firmware straight from the HEX file that the Disco utility uses, slam it in the RAVE 88S and it boots fine. One caveat, and that is the MAC address is half FF’s. The vendor side is okay but the unique unit side is not.

In the earlier firmware I did find the MAC address near offset 00007C04 in the chip. On the earlier version of the firmware I believe the MAC address was in there straight, but the newer version has FF padding in between each octet. So you will need to randomize this otherwise the use of two units on the same network switch will go south.

The flash chip is an AM29F010B in my units.

Now, one of my units for some reason doesn’t work. It doesn’t take digital audio and put it on the network. I think it RX’s fine but just won’t transmit. This is what threw me off since I was trying to do use the PRN units with this one. The second RAVE 88S, I had to hit it to get it to work (no ethernet link/no LEDs at all except one pulsing.) Technical tap they call it. After pushing down on all the seated chips (probably GAL/PAL type chips since there are versions written on them?) I haven’t had an issue. I think the unit that won’t transmit audio — it might be a SNMP value that is wrong but I haven’t spent the time to try to compare the output of snmpwalk against both units (Disco utility I think mostly uses SNMP to do all control functions.)

I was also concerned the RAVE 88S wouldn’t lock up to 44.1KHz and would require 48KHz bitrate. This isn’t true, it has sample rate conversion internal. I’ve been driving mine with both a Denon CD player and a minidisc field recorder, single ended into the XLR.

I never did solve why Disco can’t update the firmware. I didn’t have it on an isolated network, so that might be one issue.

I do plan to try to make fan out cables from the DB-HD-15 connectors on the BASIS units to hook them to 3rd party self amplified PA speakers (the BASIS units I have are meant to only connect straight to QSC amplifiers via the dataport connector on the back, a VGA type cable (that has to have all wires in the cable separate and straight though! Cheap VGA cables not ideal – shared grounds!!))

Also, did I mention, the BASIS units are way cool!!

And in case you came here sniffing around, here is the last versions of the RAVE firmware (Note the topic of this post about bricking units trying to update firmware:
QSC RAVE Firmware Files – The last ones

Yamaha C1 Music Computer Laptop

Most vintage computers I fall into. But there was one machine that has been on my radar since I first saw one in a store when I was little. That is the mysterious Yamaha C1 laptop. It’s a 286-12 MHZ laptop that has 11 midi ports and SMPTE time code in and out. I hesitate to call it a laptop because it’s so heavy, and there is no option to battery power it. It feels heavy enough to have a battery in it, but it’s just built fairly sturdy.

I’ve had an eBay trigger setup for a few years, but it mostly triggers on people trying to sell advertisements for the machine or ECUs from Yamaha motorcycles that have C1 in the description. But finally, one came up with books and disks and the original bag, and I bid and snagged it.

The caveat is that it has a functional issue. The unit always says it’s sending video to the external display. There is a dip switch on the rear that switches between the internal LCD, or an external CGA monitor. But in the case of this machine it always says it’s going to the external. So I have to fix this.

In the meantime, I am going to scan all the documentation, archive all the floppies and have already read all of the eproms into files. I’ve also documented the power supply connector, and in the documentation have the pinout for the expansion connector slot (but not the hard drive controller header.) So I will be getting all this info together and posting it for the world at large.

In the meantime — back to the issue of the LCD not working. Randomly, perfect timing, my friend Chris Favreau sent me two huge boxes of Amiga 500 goodies. In this lot was an Amiga 1084S monitor which can do CGA. So I wired the Yamaha over to the Commodore monitor and as I expected, there is no output. I never hear a floppy seek so my suspicion is the computer isn’t booting at all.

It’s been sitting open on the kitchen counter for a good while next to a few other projects getting attention. Last night I started really looking around the motherboard, and something I looked for originally but missed is the case. The green electrolytic capacitors look to have leaked some electrolyte. This means two things. First, the capacitors have probably lost their properties and might be causing the machine to not function properly (I assume they’re noise filtering but not sure.) The second — worse part — is the electrolyte is often corrosive. I think I can see a trace that is damaged by this. So the next step is going to be to replace all of the 47uf 25v green caps with replacements, and if the one trace is indeed bad I’m going to have to jumper it if it goes anywhere important. It looks like it just goes to the expansion interface slot — so if it dead ends at the expansion slot connector it’s not a big deal. But I won’t know until the motherboard has been removed. So. Many. Screws.

In the end I’m glad to have found something that looks like it could be the issue. I heard of someone else with the exact issue (External CRT always no matter switch position, and non functioning perhaps.) Electrolytic caps are probably the #1 failure of all electronics so not totally unexpected.

—[ UPDATE 7/5/2015 ]—

I replaced the 9 x 47uf 25v electrolytic caps that were leaking in the system. I cleaned up the board and tested the traces that looked like they have some corrosion from the leaked electrolyte and they seem to still function. The bad news is the system still seems to not be posting at all. No floppy seek and it’s still stuck saying external CRT when the dip switch is set for internal LCD.

The rear panel dip switch #1, on one side is connected to ground. The other side hits resistor pack PA12 near the keyboard connector, then goes on to IC52 which presumably reads it. So it’s probably read by software.

I sent an email to Yamaha USA asking about schematics. This normally does not work with any large corporation, but we will see. Anyone that has one of these systems working, you’re at risk of damage from capacitors leaking. This system I think was stored sitting upright, so the electrolyte managed to go through the board and run down the back.

Next up is I don’t know. I might look into the inverter stuff for the LCD, the sub-board. I will also wait to hear from Yamaha.

—[ UPDATE 10/2/2015 ]—

Okay this thing has been on the counter too long. I re-capped the LCD inverter board, still no signs of life. There is no disk seek on startup, which makes me think the computer isn’t executing code. I found online someone else talking of having the same issue. I looked at the motherboard more, trying to inspect for damage from the traces that show slight corrosion from the electrolyte leaking. But nothing really stands out.

Another thought that hit my mind is I’ve heard that some EPROMs lose data over long periods of time. So perhaps the BIOS chips are corrupted? It might come down to having to find a working machine to compare. Looking in the data it does appear there could be corruption. The name Phoenix Technologies has the first letter as a C in one ROM, another character in the other. Bitrot might be the issue.

I dug out the o-scope and looking at one of the BIOS EPROMs I see activity on all data lines, all address lines and the OE pin constantly. Not sure if this is normal, since no working unit to compare against. The lack of any normal ISA slot means there is no way to plug in any of the POST code debugging boards that existed for ISA slotted computers of this era.


Here are some pictures of inside the Yamaha:

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