Products > Test Equipment
HP 5335A Timer / Counter - Anything i should know?
Dr. Frank:
Some pictures of the hacks, of the PCB, options, versions and the general condition of the instrument would be nice, anyhow.
THX
Frank
David Aurora:
Yeah, I'll do a proper look check of caps etc at some point soon, safe to say given the age it will need some love like that. Fan wiring looks shocking, so I'll assume that was someones crack at the mod. Rear relay section looks clean from the top, though I did pull it and clean pins as a quick check for other issues.
Option wise it has everything except the DVM. General condition is good, but yeah- definitely has some front end issues that have been swept under the rug and shoehorned into basic operation.
I did a little troubleshooting late last night and the signal never makes it out of A12 alive on channel A. Signal is present on channel B at the output of Q4 and off to the next board, but dead on Q12. Coax had been crossed from A12 channel A to A11 channel B and vice versa, so I guess they were running it around the damaged input channel and that's why I had to hit those settings as well as why those measurements like slew didn't work.
Jumping back I found the signal was already dead at the output of U4, EXCEPT if I set the trigger control to minimum (just clicked out of preset). In that state the waveforms match between channels, but as I raise it the signal disappears. Trigger adjustment control itself works fine and ATL signal appears correct. I stopped there, I'll try to get in a bit further on my lunch break if I get a chance, but that definitely gives me some suspicions to check.
TERRA Operative:
Another thing to check as a matter of course, especially on abused units is the 50ohm termination resistors, they can end up burnt out if care wasn't taken.
I have an entire spare working unit not to be parted out (sans display window.. why do people use harsh chemicals to clean these???) but I'm not sure if I have accumulated any spare PCB's yet.. If I come across any in my piles of gear, I'll let you know. The input chips are the special ones and can be hard to find.
David Aurora:
--- Quote from: TERRA Operative on May 24, 2023, 03:39:27 am ---Another thing to check as a matter of course, especially on abused units is the 50ohm termination resistors, they can end up burnt out if care wasn't taken.
I have an entire spare working unit not to be parted out (sans display window.. why do people use harsh chemicals to clean these???) but I'm not sure if I have accumulated any spare PCB's yet.. If I come across any in my piles of gear, I'll let you know. The input chips are the special ones and can be hard to find.
--- End quote ---
Thanks!
I'm thinking if I hit a wall on ICs I may steal from the B channel to get a fully functional A channel as a temporary solution so I can at least test the main functions properly.
David Aurora:
Confirmed, U5 is cooked. Good thing I haggled when I bought this, I was told it was working properly but went in assuming it was a crapshoot.
And so the chip hunt begins!
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