I had a problem with the power amp section of a Sansui-1000A. trying to restore this thing. upon voltage check the supplies voltages are okay except of the things in red mark values. This is common to both channels. Clean tube pins and connectors and interchange the 2 tube and still got the same reading. Change coupling caps and still can't get the same DCV Value (In Black).
What seems to be the problem, need your help please?
What seems to be the problem, need your help please?
Attachments
I tried measuring resistances and still same readings .voltage readings are very far from the said value. I also guessing that it was the tubes but it happens to both channels. I just want to try 6GH8A but they don't have the same pinouts.
I tries to lowered the value of plate resistance of the pentode and reads higher but VG2 still peg at 20v. Lowered VG2 resistor to half but it pulls down the plate voltage again to 25v so remove the resistor and back to 60vdc plate. tried to play music, it sounds but too weak.
I tries to lowered the value of plate resistance of the pentode and reads higher but VG2 still peg at 20v. Lowered VG2 resistor to half but it pulls down the plate voltage again to 25v so remove the resistor and back to 60vdc plate. tried to play music, it sounds but too weak.
At first, what is your voltage meter ? What is it's input resistance ?
Supply voltage is indicated in red marks. I tried to put 500k on grid 1 to ground but no effect.
Here is something wrong
Mona
Yes those are the original values and reading are not in conformance against original voltages. Even in the cathode of the triode. So i wander why?
Yes not really in conformance. I use fluke and sanwa dmm. I tried measuring those voltages several times and this is the actual voltages im getting. When i remo remove the tube and measure plate volage after plte resistor its good as the source of 167v. On saturday i will be using another set of dmm to monitor every nodes,
Your voltages (in red) are right if you supose the anode resistor of the concertina is 182k.The voltages on the input pentode are to low all together, but that is another question. MonaYes those are the original values and reading are not in conformance against original voltages. Even in the cathode of the triode. So i wander why?
I had tried to put another 100k in parallel with 150k. The pentode plate reads close to 70v and catho is around 1.5 v but vg2 pegs at 22v. Triode is at the same mode. I trird to inject music it sounds but weak. Before the sound is nothing but hum.
Thanks for the tip i try to
Look on that, i didnt touch on triode yet since my time was wasted in the pentode. I check on the cathode cap and seems not shorted since the resistor value is read. I will try to disconnect it fot testing.
Thanks for the tip i try to
Look on that, i didnt touch on triode yet since my time was wasted in the pentode. I check on the cathode cap and seems not shorted since the resistor value is read. I will try to disconnect it fot testing.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
- Home
- Amplifiers
- Tubes / Valves
- 6AN8 Pre & concertina, what seems to be the problem?