DeWald c-800

6/25/2011 7:20:40 PMRobert Kyvig

My wife recently purchased one of these at a local ham swapmeet.

It warms up and then has a very loud hum. I can tune in local radio stations, but the hum doesn't go away.

Any suggestions?

6/25/2011 7:26:30 PMLewis L.

:My wife recently purchased one of these at a local ham swapmeet.
:
:It warms up and then has a very loud hum. I can tune in local radio stations, but the hum doesn't go away.
:
:Any suggestions?

Shound like to me it is shouting: "Recap Me! Recap Me!", especially the filter capacitors. Now I will look at the schematic and see what else it might be sayint.
Lewis
:

6/25/2011 7:30:14 PMWarren

Replace the electrolytic filter capacitors.

6/25/2011 7:30:19 PMWarren

Replace the electrolytic filter capacitors.

6/27/2011 9:08:08 PMJill Kyvig

:Replace the electrolytic filter capacitors.
:
I am looking at the schematic, and I cannot find any capacitors that are labeled specifically "electrolytic filter capacitors. Can you tell me which ones that might be? Is there another name for them?

6/27/2011 10:06:11 PMWarren

Off of pin 8 of the 35Z5 there is two capacitors. One is an 80 MFD and the other is 40 MFD.

6/27/2011 10:37:47 PMWarren P/S follow up

This is a round metal can that sits on top of the chassis. It is probably a 3 section Electrolytic. The values and voltage is on the side of the can. The 80 MFD is the square symbol on the bottom of the can by the pin. The 40 MFD is the pyramid symbol on the bottom of the can by the pin. There is also a 25 MFD that is connected to pin 8 of the 35L6 tube. You will have to buy 3 separate capacitors ( 80 MFD @ 160 VDC ) ( 40 MFD @ 160 VDC ) ( 25 MFD @ 25 VDC ) All of the new capacitors share the same common chassis ground ( negative end ) Disconnect the wires from the old capacitor can. Solder wires to new capacitors. ( positive ends )

6/28/2011 12:33:44 PMBill G.

::Replace the electrolytic filter capacitors.
::
:I am looking at the schematic, and I cannot find any capacitors that are labeled specifically "electrolytic filter capacitors. Can you tell me which ones that might be? Is there another name for them?
:
:
:
Hi Jill and Warren,
The C800 doesn't have a metal can. The filter capacitor is a big thing under the chassis. It is hard to miss.
If it had been replaced in the past, it may have been replaced by two capacitors. One will be off pin 8 of the 35Z5GT the other will be at the other end of a resistor from that pin 8. I think the resistor is 560 ohms.

All the Best,

Bill

6/28/2011 1:58:58 PMJill

::Replace the electrolytic filter capacitors.
::
:I am looking at the schematic, and I cannot find any capacitors that are labeled specifically "electrolytic filter capacitors. Can you tell me which ones that might be? Is there another name for them?
:
:
:
Thanks guys - I am obviously still learning. . . .