Wavetek 178 need repair

[Daxxin]

who experiencd this before? really no idea where to start , power supply rails is fine checked alredy.
how to check the optocouplers?

[Stray Electron]

  It sounds like the CPU isn't starting properly.  Is it in a socket? If so I would check the connections VERY carefully.  I've found that the IC sockets are a big problem in older equipment. The socket and the IC pins are usually made of different material and over time, the different materials cause corrosion.  Exposure to humidity will make it worse.  Check your clock and power signals ON THE CPU PINS and not on the socket or anywhere else. If the power and clock are ok then look for a stuck data or address bit or a bad connection to one of those pins. 

  A Fluke 9010 Troubleshooter with the proper CPU pod is GREAT for troubleshooting microprocessor based systems like this.  But they're become collector's items.

[Daxxin]

Thanks Stray Electron your info very useful , comparing schematic to board something look wrong the U45 must be an static ram but i found an intel eprom B2716
and U44 must be an 27128 but i found an national eprom NM2716Q tried to read both but they are empty , so maybe owner befor replaced with no sense.
I guess will be hard to find the binary to load in the eprom.

[Cyberdragon]

I think they just wore out and blew. The UV widows are covered meaning they probably had data at some point.

[PA0PBZ]

I guess will be hard to find the binary to load in the eprom.

I have a working one so I could read the contents and post it. Any idea if there is more firmware that should match in version or is this the only eprom?

[Daxxin]

thanks very much PA0PBZ , there is another cpu (6803) front panel board with its eprom but there no stickers no idea what version , and there no others roms around
board label its a rev. P here attached rom file from fp board

[PA0PBZ]

Well, that got interesting. Here's my 178:



Both eproms are 2716, and I checked the documentation I have but that also shows a RAM chip. If I pull both chips it does what you see: 15 times 'selftest' and then the 'prw-on-err restart'. While reading U45 was no problem, U44 gave me mostly 00's until I increased VPP to 5.5V. Now I get consistent results so I hope the file is correct.
I thought of checking the bin file by burning it into another 2716 but all I could find are 25V VPP ones and my minipro only goes up to 21V.
Anyway, see attachments and let us know.

[Daxxin]

I have also tl866cs programmer but to reflash i have bring back my old chipmax from eetools that supports this roms
Well now sometime restarting i get same message and sometime i get reference unlocked , small progress since before i get only power_on_err  ..still some logic problem . By the way you have never connected it to gpib card? I have try but cannot get any activity. I need to investigating more ...will updating.

[Daxxin]

  Problem was U45 pin12 no more contact to ground join , soldered again and maybe lost data eprom, thanks PA0PBZ 

[PA0PBZ]

Problem was U45 pin12 no more contact to ground join , soldered again and maybe lost data eprom, thanks PA0PBZ 

Good to see! I will test GPIB this week and let you know if I can get any response.

[lmester]

Daxxin,

Do you have an external timebase connected? That is the only time that you should see the "Reference unlocked" or "Reference locked" message. Getting this message without an external timebase means that you have a problem that needs repaired.

Also, my wavetek works good on GPIB. It's the only way I can easily use it. The front panel pushbuttons are in very poor condition. Bouncy and some barely work.  It's unfortunate that they put cheap click-dome type switches on an expensive instrument.

If you're interested I can upload a copy of my control program. First you should know that I use a Prologix USB to GPIB adapter.  If you don't have a Prologix or Prologix compatible adapter the software won't work.

[PA0PBZ]

By the looks of it my U44 gave up, so I had to wait for some 12.5V programmable 2716's (AM2716B) to make a new one.
Now my Wavetek is working again, but I can't find a GPIB cable anywhere
Is this still relevant after the reply from lmester?

[Cyberdragon]

I can't find a GPIB cable anywhere

Solder wires to the board. That's what I do.