Products > Test Equipment

Hewlett Packard HP461A Wide Band Amplifier

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coppercone2:
picture 2 almost looks identical to my probe boxes lol

you are missing BNC to screw terminal for $1.27. so it fits a twisted pair more perfectly then a binding post


actually never mind, its not similar, because I made a solid oak box with cut outs for most of the coaxial connectors. Banana stuff is in a box like that still. I poured silicone rubber compound (2 part) into drill holes to make safe platforms to hold connectors. I thought they are too valuable to stay in the plastic box. I think I need to make a third box now  :). But I keep the unterminated connectors in a box for cable making, not adaptors

factory:

--- Quote from: Peter_O on April 02, 2024, 05:21:45 pm ---Yup. I have drawers of test leads etc. The trick is to use them.   :-DD

Back to the topic:

I fixed the PSU so far.
The transformer is still alive, showing the same resistances as before.  :phew:
In the end only the zehner diode whas shot. 
With one 0.5W chinesium one from my stock the PSU is running again; but the zehner is getting hot very quickly because it's only 0.5W instead of 1W.

Next step is to purchase proper zehners: Acc. to lists it's a HP 1902-0202 or ZS11213-191; 15V, 1W.

On the way I found a fault that came with the device:
Output-PIN 6 and 7 (one secondary coil) of the transformer had been connected the wrong way. :scared:
That's interesting because the wire connection at the transformator looked original 70's style and the wires looked original. Is it possible, that it had been wired wrongly at the factory?

Here the faulty wiring:



Anyhow. Now it matches basic logic, the schematics and the manual too, which states "red" at PIN 6.

When the proper zehner is in, we'll see, if the transformer stays cold.

--- End quote ---

I've still got mine here (462A) if you need any readings, it seems obvious now but must have been the last thing you suspected, mine has the centre tap going to the red wire and the two outer ones (the same colors) going to the rectifiers.

David

Peter_O:
Thx for providing the pic, David!

Interestingly your's are different pcbs:
The PSU board showing the vintage HP-logo and different connections,  and the amp board with rounded tracks.
The wire colors are the same.


The zehner diode is announce to arrive today.

factory:
The PSU should be the same design, the older one in my 462A is the "OR" or original version, the newer board in your 461A is revision A. Interesting the older PSU seems to have all the traces on the back, the newer one a mix with them on both sides.

The amp boards have different part numbers, one being 00461-66502 (Rev C) & the other 00462-66502 (Rev A) for obvious reasons. The later boards all got redesigned at some point, to use straight traces & sharp corners, most products from the 1960s that were made for many years, had these changes.

There are more the pictures of my 462A attached to reply #22, if you want to see the differences.

David

coppercone2:
someone else got into it

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