Help with Collins 356A rack-up

[athnony]

Hey all, originally posted this in the wrong board.. whoops.

I was hoping to get some help on a rack-up I'm stuck on. My main issue is I'm getting very, very low output signal that seems to stem from a problem near T202 + V202.

I'm seeing T202 pin 1 has 0VDC, T202 pin 2 shows 255VDC. This makes me assume that winding is cooked, but hopefully I'm wrong? - Upon further testing this winding is reading as open on both of my units, so unless there's some magic I don't know about I'm assuming I'll need another OT...?

I also came across these comments from Doug:

Required iso diodes to avoid latch-up through shared A-/B-

The iso diodes were not added at the time of the pics, they are in series with B+ and filament if I recall correctly. Seems confusing now, possible it's only the B+, unless I modified the filament supply for higher voltage, which I may have.

My B+ PSU is one of those International Power IHB250 @ 273VDC. Will one 1N4004 in series be fine? I'm curious what could've caused that winding to go out on both units.

 

[emrr]

bummer, sorry. Age, storage conditions, too much current draw (multiple possibilities).

You only need diode iso if you are having PSU interactions.

 

[athnony]

They were in pretty rough condition when I got em so that makes sense.

Thanks for chiming in Doug.

 

[athnony]

Here's a question: I included a DI using a switched 1/4" jack that taps straight into pin 1 of v201, bypassing the input transformer. It sounds great (especially on bass) but could it cause any issues?

I've gotten kind of paranoid with these output transformers being so rare... I can't imagine it hurting but my self-taught electronics knowledge is limited.

 

[emrr]

Shouldn’t be a problem. Biggest worry is what the additional wire run does to response and noise.

 

[athnony]

Nice, I luckily haven't run into any issues with noise. Again, thanks for the knowledge Doug!