• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

New to me 610II - Distortion

OK..another observation....I thought it did nothing before but maybe I didn't notice or something but the main direct switch does make a difference. When its in the off position I can hear garbled distorted noise. When its in on position it mutes it to the point it almost cuts it off. This may because its turning down the loudness.??
 
Kapco said:
Should the cases (collectors) of the OTs for TR503&504 have continuity to ground (chassis)?
Click to expand...
Hell no... Did you remember to use the mica insulators ? And none conductive thermal compound ?
 
While trying to adjust anything. No input,No load and min. volume.
 
Yes..mica is installed and non conductive thermal compound.

OK...here's the deal with OTs collector to chassis
TR501- + on collector &- to chassis =open circuit
Flip them and I get continuity
Same with TR502

TR503 is the opposite. + on collector, - to chassis gets continuity. Flip the dmm leads and open cct. Same with TR 504

I'm thinking this is just going back down the rails, through the bridge diode and to the chassis"0" tap? That's why I need to flip the leads to get past the other bridge diode?
 
If I put the volume low...after a min or so I can start to hear the music come through. As soon as I turn up the volume and then go back to say "2" its dead quiet...then after a min I can hear music very quiet.
 
Last edited:
Have a close up look at the output transistor sockets solder connections to the main board. Reflow the solder connections with a bit of fresh solder.
 
Got back from work trip yesterday and decided to put some more time into this amp.
Tried reflowing...no difference.
I would like to test this amp by bypassing all the "junk" that could cause issues. Could I take an input signal and put it to chassis ground and the signal directly to the negative side of C481 or C482 cap? If I knew what R481value was I think I could put in a fixed resistor to dampen the volume and see if the amp produced a better output, eliminating the entire Input stage?? I just find it strange that both channels are the same....
 
Last edited:
UPDATE:- I re flowed anything that looked suspect. No change.
I decided to put the input straight into C481 to see what the result would be skipping all the input "stuff". Exact same thing. I am assuming I can rule out the input...unless something is shorted as I didnt remove C481 to test it.
So I guess since its the same on both channels, not coming from the input stage it must be something that ties them together. I think I need to re look at why I cant bias these damn OTs. everything seems to test good but somethings not right.
I got to get some :real" work done this week, but ill try and continue with it if I get a spare moments.
This amp may become an ebay part out special soon enough....
 
Haha..reviving a two year old post. I shelved the amp as I got busy with other things...decided to dive back into it. Since then I have some new equipment to help. I hooked up my oscilloscope and signal generator. Set it at 1khz/0.5v and compared the input signal to the output signal with a speaker load. See photo. Purple is signal in...yellow is output. If speaker is disconnected the output waveform turns good like the input. I'm think it's power supply. Only problem is I appear to have the right voltages on the rails to the OT and right voltage at the transformer....
Any ideas?
 

Attachments

  • 20210125_012749.jpg
    20210125_012749.jpg
    159.6 KB · Views: 10
Tried a few speakers...no major change.
I included a video link to see what's going on. Almost seems like transformer can't keep up but when I watch the rail Voltage it doesn't move much. Voltage stays pretty constant.

As you can see in the video as you turn down the volume the changes to the output.
I am going to check my diodes. Caps have been replaced and seem fine.

 
Check the collector and base voltage on the outputs and drivers..
 
When you say drivers..are you referring to the transistors that "control" the output transistors? As far as output transistors collector is sitting at the right voltages. Nothing at any of the bases I can see when measured reference to ground.
 
You must log in or register to reply here.
Back
Top Bottom