Hi

I am pretty new at this but here it goes. I recapped the radio/phono, powered up and the radio worked well. After a maybe a minute of radio (post warm up) sounds great then I get a hum. This does not change with volume, if you turn it up you really cant hear it when you turn the volume down even all the way it is there. Again for the first minute no hum sounds great. Also if I switch to phono same hum. I also disconnected both power and pick up to phono same reults. Any ideas? Thanks Jeff

Did you install any electrolytics backwards? Could also be a heater to cathode short or some other thermal related short.

T.

:Did you install any electrolytics backwards? Could also be a heater to cathode short or some other thermal related short.
:
:T.
Quite sure I did not but will check this evening. Are you thinking thermal because of the time delay?

:Quite sure I did not but will check this evening. Are you thinking thermal because of the time delay?

Yes - since there is a time-delay, logically you'd consider something heat-induced. If you have access to a tube tester - check all the tubes (allowing time for them to reach operating temp before actual testing). Alternatively, you could swap out the tubes - one at a time - if you have spares available. Other components to check would include the resistors - they can drift out of tolerance when "warmed up". Good Luck...

Almost forgot - a certain pecentage (albeit small) of "new" capacitors are going to be defective. If you've exhausted all other possible factors, reappraise your "new" capacitors....

:Almost forgot - a certain pecentage (albeit small) of "new" capacitors are going to be defective. If you've exhausted all other possible factors, reappraise your "new" capacitors....

Will Do thanks for the help. Jeff

Many tube testers tie all of the grids and the plate together, so under normal settings you will not find shorts between them--only shorts between the cathode and the control grid. After you are done performing an initial test, first throw the cathode lever up into the plate position. This will expose any cathode to heater shorts. Then throw the cathode lever down to its normal position and alternately throw down each of the grids, and finally the plate, to check for shorts between each of these elements.

Do all of this with the tube fully heated. Tap the tube if you must. This will expose microphonic shorts.

Some tube testers with individual pin throw levers will vary from this format. Up, center, and down might have different meanings with those testers. With the EICO 625 (the tester I own), normally the grids and plate are thrown up, and the cathode is thrown down, as well as filament return. The other side of the filament is thrown to the center. When a shorts test is made, it is made between the elements that are up and the elements that are down. If two elements are in the up position, they are already tied together, and aren't connected across the "shorts" circuit, and so one of them must be thrown to the down position in order to detect a short between that element and the other element lying next to it.

......Some tube testers don't have throw levers at all. With those testers I could only make suggestions based on a schematic, if one is available.

T.