Hi,
I have attached schematic of low voltage regulator that feeds phono section. It should output approx 26 volts coming out of TR342/TR343 collectors . Instead I'm getting full rail voltage of 55 volts. According to schematic voltage going to emitters of TR342/TR343 should be around 49.5 volts, but as mentioned I'm getting rail voltage. Where should I look?
I've changed pass transistors TR342/343 ,zeners and capacitors as highlighted on the attachment.
Please advise.
Thanks in advance.
I have attached schematic of low voltage regulator that feeds phono section. It should output approx 26 volts coming out of TR342/TR343 collectors . Instead I'm getting full rail voltage of 55 volts. According to schematic voltage going to emitters of TR342/TR343 should be around 49.5 volts, but as mentioned I'm getting rail voltage. Where should I look?
I've changed pass transistors TR342/343 ,zeners and capacitors as highlighted on the attachment.
Please advise.
Thanks in advance.
TR 342, 343 are constant cuurent sources and will give full voltage without their specified load.
Thanks for all the replies.
TR342/343 were really hot and so I was afraid there was a short somewhere. I'm away from the amplifier now,but I think I measured the full rail voltages while the B+/B- was connected to the phono section. Are you suggesting there might be some fault on the phono section? What should I check?
Thanks all
TR342/343 were really hot and so I was afraid there was a short somewhere. I'm away from the amplifier now,but I think I measured the full rail voltages while the B+/B- was connected to the phono section. Are you suggesting there might be some fault on the phono section? What should I check?
Thanks all
Very nice example of shunt regulator. Output should be at or near 24 volts.
If not check TR119, 120 , zeners D106, 107 and associated caps.
If not check TR119, 120 , zeners D106, 107 and associated caps.
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Hi,
Phono section is playing nicely now. Silly mistake on my part. The phono input impedance selector switch was all gummed up and didn't pass a signal. I cleaned it and all is good.
I would like assistance on a second issue.
When "Main Direct" is off (tone controls are activated), I get AC hum. Not loud,but annoying. When "Main Direct" is on (tone controls bypassed) the amp is silent.
I took a chance and replaced C219/220 (0.22uf/50v) on Tone Control 2 in schematic,but alas no change. Any suggestions where to look or what might be suspect?
Thanks in advance
Phono section is playing nicely now. Silly mistake on my part. The phono input impedance selector switch was all gummed up and didn't pass a signal. I cleaned it and all is good.
I would like assistance on a second issue.
When "Main Direct" is off (tone controls are activated), I get AC hum. Not loud,but annoying. When "Main Direct" is on (tone controls bypassed) the amp is silent.
I took a chance and replaced C219/220 (0.22uf/50v) on Tone Control 2 in schematic,but alas no change. Any suggestions where to look or what might be suspect?
Thanks in advance
Attachments
Hi,
There was no sound coming from phono section so when I disconnected the supply to the phono board and measured rail voltages I was sure the board got fried by this high voltage.
Supply voltage returned to normal once reconnected and sound came back once the input impedance selector switch contacts were cleaned.
Thanks for all the help.
Now ,if someone could help me with the hum issue that would be great. Could it be that the main caps are failing?
Regards
There was no sound coming from phono section so when I disconnected the supply to the phono board and measured rail voltages I was sure the board got fried by this high voltage.
Supply voltage returned to normal once reconnected and sound came back once the input impedance selector switch contacts were cleaned.
Thanks for all the help.
Now ,if someone could help me with the hum issue that would be great. Could it be that the main caps are failing?
Regards