TDS430A Attenuator replacement

[dan3460]

I got this scope a few day ago and today I started to work on it. Took me almos 2 hours to clean this thing, it looked like was left on a barn and had a ton of dust. I took the cover, made sure that power supply looked ok and also checked the lytics on the main board, every thing looks ok. I fired up the scope came to life but had 1 fail - Acq/Attn. I followed the troubleshooting procedure and it say to replace the acquisition board, which I suspected.
Started to search for the problem, channel 2 I can get full signal. So I wired my signal generator to put the same signal into both channels so I can compare the path as I don't think there is a full schematics for this thing out there. I also setup both channel at the same amplitud, 1V and the signal was a square 3Vpp.
Probing the path in both channels I came to a place where was different, actually was signal on channel 2 but nothing on channel one. It is right at the end of the path trough the attenuator, looking at the attenuators from the bottom and counting the pins from back to front is pin #2. On Channel 2 is a signal about 150mv in amplitude, in channel 1 is a flat line about -250mV. I pushed a square wave about 300 mVpp into pin#2 and the scope displays a square wave on channel 1. So clearly is the attenuator, more specific the hybrid sitting there. So my questions are:
1- Can the hybrid be replaced?
2- Can something be put together to replace the hybrid?
3- Can I use an attenuator from other 400 series of scopes, on ebay is a cheap 420?

Suggestions welcomed.

[TAMHAN]

Hello,
for this kind of detail questions, the Yahoo Group of Tek owners AFAIK is better. There are a lot of Ex Tek guys there...

[dan3460]

I posted the question on the Tek group but I have not gotten any answers. My urgent question at this point is if a attenuator from a 420 would work on this scope? The 420 is a 100 MHz scope (I think) and this one is 400 Mhz.

[voltsandjolts]

FWIW I have replaced an input hybrid on a TDS3034B and it worked - so, no verification of the input ASIC serial number by the main board.

For 70 bucks this has got to be worth a try?
http://www.ebay.com/itm/Tektronix-TDS420a-circuit-board-assy-attenuator-671-3595-00-/322350570742?hash=item4b0d975cf6:g:UkgAAOSwZVlXn~lZ

[dan3460]

I have a TDS420A that I purchased for $25. My main concern is not that it will work, is that the design of the attenuator will not take 400MHz. I just wanted to get assurance before I go taking the attenuator from the 420 (200 Mhz) and putting it on the 430, there is a lot of pins to de-solder.