Hmm.. that's not acceptable..
New guy vs CR-840
- Thread starter Kirk V9
- Start date
How "close", and on DBT?
Thats why its low. Its the DBT loading down the AC input.
Kirk V9
New Member
Sorry work term. They tested fine both with multimeter and component tester.
Kirk V9
New Member
should I do the readings again off the DBT?
I'd be changing that other bulging cap you mentioned in the protection circuit first. But wait until avionic gets back to you before powering it up again. He may be into something.
Kirk V9
New Member
Quick update while I’m at the Doc’s.
Changed out the two caps in the Protect Circuit because they looked a little bulged (one more than the other). Both tested a higher capacitance than expected.
I then applied power through the DBT without any drama and then applied regular power and got the relay to engage and disengage several times with the power switch on/off.
I will get the transistor readings in the power supply circuit when I get home.
A little more progress.
Changed out the two caps in the Protect Circuit because they looked a little bulged (one more than the other). Both tested a higher capacitance than expected.
I then applied power through the DBT without any drama and then applied regular power and got the relay to engage and disengage several times with the power switch on/off.
I will get the transistor readings in the power supply circuit when I get home.
A little more progress.
That's good news indeed. With the relay engaged, you should now be able to check the DC offset at the speaker terminals. That will tell a lot about the amp's overall health. But making sure all the voltages are good throughout still needs to be confirmed.
Kirk V9
New Member
Plugged her in again and fired it up without the DBT. Relay engaged and it sat peacefully for 30 minutes then I took some readings.
TR801 E: 44VDC
C: 68.3
B: 44.5
TR802 E: -46.5 VDC
C: -68.7
B: -47
TR803 E: 0 VDC
C: 44.3
B: 44.1
TR804 E: - 6.1 VDC
C: -47.0
B: -6.7
TR805 E: 32 VDC
C: 34
B: 32.6
DC OFFSET (measured on 200mV scale) I've never done one of these before BTW so my confidence in the readings is low. These are the spring loaded speaker connecting and not RCA or Banana plug. I touched the probes to the visible metal contact and not opening up the connector and inserting the probe.
Channel A L: 0.00
R: 0.00-0.03 Fluctuating then settling out at 0
Channel B L: 0.01
R: 0.00
I know that the offset is supposed to be as low as possible but I was expecting something more than this for a unit that had obviously never been serviced in 40ish years.
That's where I am at now.
TR801 E: 44VDC
C: 68.3
B: 44.5
TR802 E: -46.5 VDC
C: -68.7
B: -47
TR803 E: 0 VDC
C: 44.3
B: 44.1
TR804 E: - 6.1 VDC
C: -47.0
B: -6.7
TR805 E: 32 VDC
C: 34
B: 32.6
DC OFFSET (measured on 200mV scale) I've never done one of these before BTW so my confidence in the readings is low. These are the spring loaded speaker connecting and not RCA or Banana plug. I touched the probes to the visible metal contact and not opening up the connector and inserting the probe.
Channel A L: 0.00
R: 0.00-0.03 Fluctuating then settling out at 0
Channel B L: 0.01
R: 0.00
I know that the offset is supposed to be as low as possible but I was expecting something more than this for a unit that had obviously never been serviced in 40ish years.
That's where I am at now.
Kirk V9
New Member
Am I ready to try that?
Kirk V9
New Member
Yep it was sitting powered on for 30ish minutes after the relay click. I then measured the transistor voltages and then the DC offset.
The only issues that I am aware of now before trying anything is that there aren’t any lights besides the LEDs.
Most likely just a burnt out incandescent lamp 12v@60ma
Contact DGWOJO Dave will hook u up with the correct lamp. He is also and active AK'r.
https://sites.google.com/site/dgwojocom/
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Kirk V9
New Member
Ok well then I’ll hook it up to some speakers and a CD player and give it a whirl. Oh and I’ll get a fire extinguisher ready too. Haha
