C-4 pre. Both outputs are failing.

rockman

rockman

Active Member
Hi
My newly acquired C-4 ,which I was so pleased with, has started to fail on the 2 output channels.I have done the deoxit spray on the switches,with the amp dismantled,but to no avail.
This is all it takes to knock out the whole system.


Can anyone help as to what to do that will be positive.Maybe Avionic.Be nice to hear from ........
Thanks All

Rockman:tears:
 
C4 Pre Bothoutput are failing

Hello

Do you mean both channels quiet ?

Did you check if all voltages are OK in power supply ?
 
rockman said:
Hi
My newly acquired C-4 ,which I was so pleased with, has started to fail on the 2 output channels.I have done the deoxit spray on the switches,with the amp dismantled,but to no avail.
This is all it takes to knock out the whole system.


Can anyone help as to what to do that will be positive.Maybe Avionic.Be nice to hear from ........
Thanks All

Rockman:tears:
Click to expand...

Bummer...Do you get any lamps illuminated ? Do you know how to use a multimeter ?. Down load the SM. and check the +/- 30 volt adjustment. I believe it is step one in the adjustments table.
 
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output channels on C-4

Hi All

Thanks for the replies.

On output No.1,only one channel was working,now there is nothing.
On output No 2 both channels went off at almost the same time.

I am thinking of getting this professionally looked at.

Thanks again

Rockman.
 
This really sucks. After all the problems that you had with your C-70 now this. I'm very sorry to hear this Rockman. I hope that you're able to get it sorted out without any major problems.

Cheers,
James
 
rockman said:
Hi All

Thanks for the replies.

On output No.1,only one channel was working,now there is nothing.
On output No 2 both channels went off at almost the same time.

I am thinking of getting this professionally looked at.

Thanks again

Rockman.
Click to expand...
If you decide to go that route I recommend finding an AK'er to refurbish it. Where are you located?
 
C-4

Hi All

Thanks again for your help
.I am in the UK,not far from London.I have sent photos today to specialist outfit who will contact me again tomorrow.

Regards

Rockman.
 
I've worked on a few of these and one big problem I've seen on 4 out of 5 that I've seen has been a cracked board and broken traces underneath of these two heat sinks. They come loose and eventually it breaks the circuit.
 

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Zombie thread !! 8 years old, that's the thing with the new format showing "Similar threads" below the existing thread, many do not notice the dates.


It might help some one tho searching, so I guess ....eh what the hell !! :D

Nashou
 
Ftlbs said:
I've worked on a few of these and one big problem I've seen on 4 out of 5 that I've seen has been a cracked board and broken traces underneath of these two heat sinks. They come loose and eventually it breaks the circuit.
Click to expand...

1687909958773.png



Obviously that is not a C-4.!... C-60/65 perhaps.. The C-4 has thicker PCB's ..

Both the C-4 and the C-60/65 & C-80/85 are also plagued with glue in and around those regulator pass transistors and there heatsinks.


Always a good idea to remove these transistors & heatsinks.. Erradicate the glue and glue damage. Regrease the transistors and re-install.
Scotchbrite cleans the oxidation off those heatsinks real quick.
 
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Correct image of the bottom of that board and the damage I've found.
 

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And I just saw the zombie thread. I swear I didn't see the dates. Too many meds maybe. I'm going to bed now......
 
Ftlbs said:
Correct image of the bottom of that board and the damage I've found.
Click to expand...
I guess your just the lucky one. Out of the last 25 or so C-4's. I've never seen it broken like that.

That is shipping damage !
 
Lucky me I guess. The ones I've seen looked like they'd been that way for awhile. Two of them even had the cords cut. I repaired the traces and they fired right up and worked fine. I went over the suspicious solders, cleaned everything and so far no issues. I sold a couple and kept two for myself. Absolutely love these so much that I swapped out my C-85 for it in my main system.
 
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