Update on the HP 5340A.
Replacement capacitors assembled & fitted.
All low voltages checked & verified as good. I left the Sangamo caps as they tested OK and didn't have crust underneath or that fishy smell, all the failed caps were Sprague, two of which were shorted.
It now has at least two other problems, first one is the display supply (+175V) is low & the displays dim or barely lit at a result. It's below the 135V-ish that the book states most voltmeters will display, as no smoothing cap is used.
The second problem, the displays are mostly stuck on 7s in self check mode, need to fix problem one first.
David
Ooh, I should get back onto fixing mine, I have a nixie version (actually two of them, and a third that was firmly a parts unit that got stripped down).
I just replaced those PSU caps with new Japanese ones of the same form factor, the original ones were so old and dried out that some sounded like they were full of dirt!
I've made reproduction OCXO Option PSU boards ready to populate one when I get to it, as I came across the needed transformer in the parts unit. Still have to source the actual OCXO though.
I'm definitely looking forward to seeing if the 18GHz inputs have been blown or not.... Hopefully I can cobble a fully working unit from the parts I have on hand..
I'd love to get my hands on the upgraded input section that was reportedly much more resilient, but that seems practically unobtanium unless you luck across it somehow.
Guess I sort of had some luck there, as both of mine seem to have been updated with the later front end assemblies, but both arrived in quite a state.
First 5340A from Germany had lots of fasteners missing, a hole where the I/O board had been robbed and loose RF connectors in the front end. After all those issues had been addressed, it only required the switches cleaning to work.
The second 5340A had two shorted PSU can caps, two failed rectifiers and the odd loose/missing fastener.
I couldn't easily obtain replacements screw terminal can caps, those at Mouser were quite expensive & some values were not stocked. Plus I have lots of surplus caps from the components I bought from work.
Still working on the +175V power supply, but since checking everything on the regulator board (all transistors, zeners & passives checked) I'm beginning to suspect the rectifier or transformer winding. I would check voltages against the good 5340A
but can't access it until the storage unit reopens tomorrow.
Here is the output of the transformer with red wires disconnected from the rectifier, the book states the winding is 155V (but no mention of whether that is peak-to-peak or RMS).
With the wires reconnected to the rectifier & regulator board removed, I get this on the output of the rectifier, looks odd to me. Note: the rectified supply here is added to the unregulated +15V before going to the +175V regulator board.
Note: the rectified supply above is added to the unregulated +15V before going to the +175V regulator board.
David