Tek 465 update. Got it back together. Channel 2 works perfectly. Channel 1 appears to have been fudged at some point. Going to swap the attenuator modules between channels to try and fix. If that doesn’t work then it’s donor vertical amp hunt
Edit: well fuck. Channel 1 vertical 10x is toast by the looks. There’s signs someone has tried to repair it in the past but it appears that they were unsuccessful. Next step try and find a spare vertical. Note it’s the board that is dead not the attenuator module. Grr.
Well and truly fucked.
Damn, dude... I was REALLY hoping your luck had changed with this one. No hope of kit-bashing between boards in this one and the parts mule?
Yes, I realize that this way lies madness... but... well... look where you are.
mnem
*Says a prayer to Ifni that bd139 finds "his" 465*
All is not lost
Quick photo of the arse of a Tektronix 465 attenuator for those lucky folk who never have to go digging to find it.
I found this hiding which was not a good sign. Also some shitty soldering. Someone has had the vertical out already by the looks.
So a little later than before. Decided to re-approach it from scratch. I traced through the attenuators almost to the front of the channel FET with DC and the front end attenuators. All working absolutely fine (thanks BM867s). Which was puzzling as feck because it was correlating failure on 10X. So I pulled all the attenuator modules out and worked out that the idiot who put it back together the first time had put the 10X in the 100X hole and vice versa
. Got that back in and channel 2 was spot on with no weirdness. Channel 1 still buggered. But whatever the problem was, is past the attenuators. So I looked at the schematic and there's a programmable-gain amplifier further up the chain. I looked at this as it's under the attenuator module and what did I find? Some squished looking components. So I poked around with the DMM and found the butt side of a resistor with a tubular ceramic, R49/C49 shorting against ground
Bent it back a little away from ground and you know what? It bloody works. Miracle.
Now the only thing that doesn't work on it that I can find so far is the probe indicator. Probably a duff transistor or cap that. Usually is.
Happy bd139 at last. Persistence pays off
Edit: fixed probe indicator as well. 100R series resistor shorting against panel. Sorted!