WAD 5881 - resuscitation

[tubehead]

No they're XLR, I've actually gone into the shed to check. I took some photos too. Looks like one of the caps have popped.

[tubehead]

[Richard]

Yes, nice project there

If you've not done it yet I'd start by checking the OPTX windings. Expect between 100R and 200R for the primaries (anodes) and less than 1R for the secondaries (speaker posts) looking for similar results between both TXs.

[bob orbell]

If this was my project, I would remove the PCB, all the electrolytic capacitors and discard them, wash the PCB in warm soapy water and dry with a hair dryer, remove the transformers clean and check as Richard has suggested, clean the chassis, inspect all and reassemble with new capacitors. Nice project. Bob

[tubehead]

Originally Posted by Richard

Yes, nice project there

If you've not done it yet I'd start by checking the OPTX windings. Expect between 100R and 200R for the primaries (anodes) and less than 1R for the secondaries (speaker posts) looking for similar results between both TXs.

Good idea. Not worth bring back if the transformers are kaput.
The heater wiring looks like it was added later. Not sure why, perhaps there is some issue with the pcb tracks.

There is flux all over the pcb, so I'll be washing it as suggested by Bob.

Thanks to Greg, I have the circuit diagram with test point voltages etc.

I'll update this thread when I've progressed this. I've got a couple of other projects on the go so this may take a while.

[bob orbell]

The heater wiring is correct, there are NO PCB tracks due, I suppose, to the current draw of all the valves, or simplifying the board layout. Bob

[John Caswell]

If you are going to wash the PCB in warm soapy water, which I do not suggest in any circumstance, then you will need to rinse it off with purified water or distilled water to get rid of all the chemicals in tap water, as they will deposit themselves on the valve base pins etc and cause you untold grief later as they gently corrode things.
Use IPA and a tooth brush or the like to gently scrub deposits away, then rinse off with more IPA, finally blowing away any remaining IPA with a hot air gun/hairdryer.
Be very wary when removing components, as the PCB/track adhesive was not very good on these early boards, and if the builder has bent the component leads hard against the PCB you will need a great deal of patience., or wiping dry with kitchen roll

John

[tubehead]

Originally Posted by John Caswell

If you are going to wash the PCB in warm soapy water, which I do not suggest in any circumstance, then you will need to rinse it off with purified water or distilled water to get rid of all the chemicals in tap water, as they will deposit themselves on the valve base pins etc and cause you untold grief later as they gently corrode things.
Use IPA and a tooth brush or the like to gently scrub deposits away, then rinse off with more IPA, finally blowing away any remaining IPA with a hot air gun/hairdryer.
Be very wary when removing components, as the PCB/track adhesive was not very good on these early boards, and if the builder has bent the component leads hard against the PCB you will need a great deal of patience., or wiping dry with kitchen roll

John

Ok, noted. Better to use IPA or distilled water. I think some of the tracks have lifted.

[Greg.]

Originally Posted by tubehead

I think some of the tracks have lifted.

Soldered tinned copper wire links between components where track is damaged works well.