Author Topic: Racal-Dana 5002 / ME-545/G repair  (Read 1415 times)

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Offline cprobertson1Topic starter

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Racal-Dana 5002 / ME-545/G repair
« on: March 07, 2018, 11:54:45 am »
Good Morning folks!

Link to Manual

I've just done the first wave of repairs on my Racal-Dana 5002 wideband level meter - the mains filter blew and I've since replaced it.

The unit now has power-up issues, which I've partially resolved, I'm getting an "Er 01" error showing on screen:
Quote
Er 01 displayed.
Step 1. Press RECALL key, then number 0 key twice. Enter 97 . 1 using numeric
keys. Press SHIFT then SF keys. Verify display shows <50?V and Ur.
• If incorrect, proceed with step 3.
Step 2. Using Digital Voltmeter, verify BT1 voltage > 2.5Vdc (fig. FO-2, sheet 2).
• If correct, Voltmeter is operational.
• If incorrect, replace BT1 (para 5-36).
Step 3. Troubleshoot around RAM A1U20 and U21 using (fig. FO-2, sheet 4).
• Replace faulty component.

Firstly, the battery is missing (the previous owner must have removed it) - so I've bodged in some wires so I can hook it up to the bench meter for now (I'll add in a lithium button cell holder if I have a spare kicking around somewhere)

However, even when supply the specified 3V, the error remains - so proceeding forward to step 3 - "troubleshoot the ram using FO-2-pg4"!

So - the question is this! How do I test these CY7C148 RAM ICs to confirm they are working? :-DMM?

My first instincts are to:
  • Check the voltage rails
  • Look for data (in and out)(poke with oscilloscope)
  • Check CS/WE pins
  • Dig out the logic probes

- But having said that, I've never tested a RAM IC before... RAM assemblies, sure, just use memtest.exe - but never the ICs themselves!


Stuff I've done so far (only had an hour last night before I decided to go to bed! I'll have something like six hours to look at it tonight though ;))
  • Replaced mains filter
  • Hooked battery to bench PSU (unit reliably powers up, but still gives error code 01
  • Confirmed voltage rails on board (but not at the RAM ICs
 

Offline cprobertson1Topic starter

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Re: Racal-Dana 5002 / ME-545/G repair
« Reply #1 on: March 09, 2018, 08:18:16 am »
Urgh that was a nuisance.

Ended up digging out the logic analyser.

The data entering the IC was fine, but readback was corrupted - so it either wasn't writing or reading properly - well I suppose it could actually be both.

Whatever the problem was, I've replaced it with a modern equivalent and we're up and running!

It's even been in spec for the few measurements I've made with it so far; pretty good for a 30-year old bit of free kit!
 


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