help with a GOULD 4064 4 channel DSO

[large_ghostman]

hi i have been given a broken scope that i want to have a go at repairing, ive looked round the net and isnt much in way of manuals, the scope dosnt power up as such but i get the power led on but no other front panel lights somnetimes i get a bit of a line down the left of the screen but not always, ive taken off the cover and testead the power rails and they are way way off much higher than they should be, for example i got 64v on the +12 rail, i have done nothing else so far so any sugestions?? or help fault finding it, it wou;ld be reakly cool to get it going as i am allowed to keep it if i do and its 150mgz 4 channels with alot of cool features

 

[cowboybob]

Good luck with this one. 64V on a 12V rail most probably means that every IC on that bus is toast.

Not to say "don't try". Here's some info (not complete) on a 4072/74 that it is claimed to be not that far from the 4064 in design. Apparantly the entire manual is 20MB.

View attachment Pages from 4072_pp001-018.pdf View attachment Pages from 4072_pp019-106.pdf View attachment Pages from 4072circuitpp107to181.pdf

Here's the site that has the discussion on a 4064 problem. Might help. And who has this manual.

https://www.vintage-radio.net/forum/showthread.php?t=68058

Look at post #8.

 

[large_ghostman]

thank you for the info, i am going to take off all the conections from the psu to the scope and retest the outputs on it, do i need a dummy load? if so what do i use? i have two scopes i would like to get going the other one dosnt look as bad tho, but this scope is way way better so i am trying to fix it first. also i dont take the cover off without dad there, most the very high voltage stuff is under covers and i am not allowed to take them off

 

[tvtech]

thank you for the info, i am going to take off all the conections from the psu to the scope and retest the outputs on it, do i need a dummy load? if so what do i use? i have two scopes i would like to get going the other one dosnt look as bad tho, but this scope is way way better so i am trying to fix it first. also i dont take the cover off without dad there, most the very high voltage stuff is under covers and i am not allowed to take them off

Hey Little Ghostman

Better to wait for Dad

Regards,
tvtech

 

[dr pepper]

Are you sure you measured form the correct ground, you might get 60 odd volts on the 12v rail if you were measuring from a different ground than the 12v one.

If there is 60 odd volts on the 12v rail, then as bob said I think its probably far gone.

Check your meter with a 9v battery, make sure its not just your meter.

 

[large_ghostman]

ive come back to look at this again! the rails give all kinds of readings, so i might try and rebuild the PSU as long as the transformer isnt shorted it shouldnt be to bad :S i hate it when i cant get something to work!! ive also got a scope that didnt display the waveform i changed the inductor just after the input because it was blown and now i get a trace up but it dosnt do anything, dosnt matter what signal i use the trace dosnt show it. so will have to dig around a bit

fixed the bench multi meter this weekend and now it works great!! can anyone tell me how to take 4 wire measurements with it?? i know it can do them but not sure what leads i need or how to connect them?

 

[tvtech]

Hey Buddy.

Find Dad. He will talk/walk you through it.

Regards,
tvtech

 

[large_ghostman]

dad is not what you call technical lol

 

[cowboybob]

...fixed the bench multi meter this weekend and now it works great!! can anyone tell me how to take 4 wire measurements with it?? i know it can do them but not sure what leads i need or how to connect them?

Is this what you are considering?:

https://www.electro-tech-online.com/custompdfs/2013/02/AN106.pdf

 

[large_ghostman]

hi, i should of explained better! the bench meter i fixed is a old but good RACAL with 5 1/2 digits, on it there is 5 sockets, 2 for ohms reading and 2 for volts then there is a socket marked guard. apparently the meter will do 2 or 4 wire measurments as there is a switch on the front that says 2 wire/4 wire. i just wasnt sure if i needed special probes like on my LCR meter with 4 wire, and what is the guard socket for? i also have that on the LCR

as for the little gould 400 oscilloscope i am in with a chance as i have found the service manual

 

[cowboybob]

hi, i should of explained better! the bench meter i fixed is a old but good RACAL with 5 1/2 digits, on it there is 5 sockets, 2 for ohms reading and 2 for volts then there is a socket marked guard. apparently the meter will do 2 or 4 wire measurments as there is a switch on the front that says 2 wire/4 wire. i just wasnt sure if i needed special probes like on my LCR meter with 4 wire, and what is the guard socket for? i also have that on the LCR

as for the little gould 400 oscilloscope i am in with a chance as i have found the service manual

My emphasis.

You should not need special probes for a 2/4 wire measurement.

The inputs float. The "guard" (essentially ground) is there for you to be able to "un-float" (ground) the low side input.

Don't know what model Racal you have, but maybe this would help:

**broken link removed**