It would help if you'd tell us what 'scope model you have and what you did to come to your conclusion. All kinds of things may be wrong. E.g. did you check the connections to the horizontal

The trace on the screen begins in the middle of it. I suspect the horizontal preamp 155-0124. Can someone help me? Does anyone have such a circuit? Thank you

where do i find the b trigger pickoff on this any idea?

can i feed a 1v p-p from my other scope cal into that?

It's the BNC in the upper right-hand corner. -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 http://www-smirc.stanford.edu

firstly i cant see a b external trigger input,also has anyone a pic of the component placements on the ch B trigger board ?,as i cant find one in the manual i downloaded from tek wiki,cheers all

Great -- verifying supply voltages is a good first step. Next, trace signals as they progress through the trigger chain, perhaps following up on Harvey White's good suggestion. At some point, you'll

any ideas what to check?all the psu voltages are good.

Did that once when I was impatient, to smoke out a tantalum cap that had shorted out the -15V rail :-) To make a test jig like you suggest, I would just get a card-edge connector with solder lugs

It can be lots of things, of course. I am not a fan of the "random potshot" method of repair in general. The wear and tear on a pc board from unnecessary desoldering/soldering adds up. Also, TDs can

Hi Bruce, Let's try to reduce CR262 current to see if it will go to low voltage state. 7B50 is in timebase mode (not amplifier) Triggering in NORM EXT trigger, DC coupled No input (or shorted) at EXT

All: I just picked up a MDO3102. Where Channel 3 typically would be on a four channel scope, there is a Trigger Aux In BNC. The Aux In has a VPI landing area/contacts. Does anyone here know what the

does anyone know if a bad tunell diode can cause this?,i have two spare from a 453a,i see 2 on the b trig board,one near TP675 and onother nearish to what looks like q704,any idea which is which?,ii

Don't have one, but had a similar situation with a Telequipment D75.  Triggering was very touchy, but it would somewhat trigger. Following the signal through, there was a differentiator that fed the

hi ive got issues with the triggering on my 453,firstly it wouldnt trigger on ch A or B,i washed the whole scope down in the shower and dried it,it now works fine on ch a but has a hard time

Hi Ozan, My interleaved comments below. Thanks, Barry - N4BUQ

Hi Barry, My comments are below: I assume there is still no signal (>.3V) across CR262. So far only smoking gun is voltage across CR262 not dropping to ~ 0V because of current through it cutting off.

Ozan, I'm not sure, but I may have made some mistakes in those voltage measurements (conflated one resistor with another) because I checked the voltage across L267 and it is nearly zero. I just did

Good detective work. Although I agree R394 looks a little too high and changing it should help, it is unlikely the root cause of the fault you are seeing. Your measurement of voltage difference

Thank you so much for doing that! I just brought home a 575 yesterday. It runs perfect at the moment. My 576 acts up sometimes, so it will be a nice back up.