Hi, I have a Coronado amp, which sounds great as a clean platform. The amp comes up nice and both the IN1&2 and IN 2 channels work as they should, until about 5 minutes into it.... the IN 2 Channel cuts out to very low volume. It will intermittently come back but it is sporadic. IN1&2 still operates but only the 1 side when it cuts out. It is meant to be interactive.
I have checked all tubes
Chop-sticked for any loose connections - I cannot get the amp to cut out when chop sticking or get back when it cuts out.
Cleaned the jack and pots, and tightened all pots and jacks nuts.
I believe the hand drawn schematic is closer to what I have.
The Bias resister is hitting 31vdc
I do not have a lot of experience with PCB circuits. Trying to help a fellow musician.
Any help appreciated as to what I might try.
Thanks A
Supro Coronado 1690T cuts out
Moderators: pompeiisneaks, Colossal
Supro Coronado 1690T cuts out
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Re: Supro Coronado 1690T cuts out
It can be tough when you can't get it to fail when you need it to! In the past, I've found mysterious intermittent ground connection by twisting the chassis.
Does the sound CUT in and out, or FADE in and out? Fading would indicate a heater power failure.
Does the sound CUT in and out, or FADE in and out? Fading would indicate a heater power failure.
I build and repair tube amps. http://amps.monkeymatic.com
Re: Supro Coronado 1690T cuts out
Hi Aaron, it just suddenly cuts out to very low volume on the IN2 side. I used my Big Shot ABY to goose it (both inputs connected) and got it to come back for a bit then fail. We tried running the amp for an extended period and suddenly it cam back but then failed again (on the IN2 side). It happened to the owner at a show and drove him nuts. When it cuts out it is quite dim but still there, it can come back without explanation. Chopsticking is a not showing any loose connections. ??
Best A
Best A
Re: Supro Coronado 1690T cuts out
Just carefully reflowed the two jacks, I think they are using other than 60/40 solder. Now that IN 2 does not have full volume at start up just the low level as in the cutout. Wondering if I might clean those jacks and re-solder from scratch.
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Stevem
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Re: Supro Coronado 1690T cuts out
Are the input jacks the common switchcraft type that have the built in shorting switch in them?
If so then when a cable is inserted the switch might still not be opening enough once the amp warms up to stay open.
If so then when a cable is inserted the switch might still not be opening enough once the amp warms up to stay open.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Supro Coronado 1690T cuts out
Are the input jacks the common switchcraft type that have the built in shorting switch in them?
If so then when a cable is inserted the switch might still not be opening enough once the amp warms up to stay open.
If so then when a cable is inserted the switch might still not be opening enough once the amp warms up to stay open.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Supro Coronado 1690T cuts out
Steven thanks for chiming in.
Yes they are switchcraft type, checked that aspect and the switch is opening as it should.
The amp played normally and after a few minutes it cuts out (low volume) on IN2. Since I reflowed the jack at IN2 the amp now does not play normally at startup!!
I inspected the soldering re-flow and it's looking quite normal.
Plate voltages are normal.
PCB's are vexing to work on. I hesitate to start pulling boards out, which would require de-soldering various connects.
Tremolo does work on IN1&2.
IN2 is there its just low volume, not a complete cut out.
When is put a boost pedal on the In2 jack I can get the signal up significantly (of course), and it does connect over to the IN1&2, so the jacks are fine. Something is cutting the strength of the signal. Maybe a cap gone bad?
Yes they are switchcraft type, checked that aspect and the switch is opening as it should.
The amp played normally and after a few minutes it cuts out (low volume) on IN2. Since I reflowed the jack at IN2 the amp now does not play normally at startup!!
I inspected the soldering re-flow and it's looking quite normal.
Plate voltages are normal.
PCB's are vexing to work on. I hesitate to start pulling boards out, which would require de-soldering various connects.
Tremolo does work on IN1&2.
IN2 is there its just low volume, not a complete cut out.
When is put a boost pedal on the In2 jack I can get the signal up significantly (of course), and it does connect over to the IN1&2, so the jacks are fine. Something is cutting the strength of the signal. Maybe a cap gone bad?
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Re: Supro Coronado 1690T cuts out
Ok got it, the old Freon trick on one of the bypass caps, brought it back to life. Now may still have to pull the whole damn things apart to replace that cap. Anyhooooo, thanks for the support
Best Ange
Best Ange
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Supro Coronado 1690T cuts out
It might not be the cat itself, it could be that circuit board trace.
I guess you will find out when you go to remove the suspect cap
Yes I have come across this on new gear.
I guess you will find out when you go to remove the suspect cap
Yes I have come across this on new gear.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Supro Coronado 1690T cuts out
Before I did the freon thing, I was 2/3rds of the way towards removing the boards but stopped. I reckon in order to get this board out everything has to be released, both boards, AC module and the on/off/standby board. All zips come off. All and everything yes?