Re: HP 3335A Repair

Thank you. I figured out that error, but I still can't figure out how to access the measurement points. I enclose some pics. Unless the PS PCB slides out somehow, I cannot yet figure out how to access those points.?

Not wanting to sound lazy, but I really hate terrible?engineering of servicing. Jury's still out on whether it's me not having read the entire service manual (closely enough), or whether they did a bad job at making these very serviceable.?

Radu.?

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On Fri, Sep 16, 2022 at 7:34 PM tmillermdems <tmiller11147@...> wrote:

There is an error in the manual. A16 is actually A15, the pass transistor assembly.? C1, C3, CR1, and CR2 are just below the J2 and J3 connectors.

Regards

On 9/16/2022 9:00 PM, Radu Bogdan Dicher wrote:

Working on this unit, with a non-working display, and other lights on there not making much sense. I didn't even really try to output a signal and see if it's there.?

PS a high profile suspect, obviously. All raw DC supplies look OK, all regulated supplies are low by almost about 30%. Smoking gun that is.?

So, I am working through the troubleshooting steps for Group F (p.8-F-1). If regulated supplies are off, and unregulated are OK, step two says to check A16 voltage doubler. This is supposedly done by measuring 55V between R1/CR2 and R2/CR4.?

Has anyone in the history of the 3335A been able to reach the points where measuring this is feasible? I've been bending my probes and self to figure how am I supposed to perform this measurement. Has anyone done this recently enough to recall, or versed in this unit to tell me how the heck am I supposed to measure this unreachable potential differential?

Thank you,
Radu.?

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