Please Help ID Prob w/Bogner 101B 20th Ann
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Please Help ID Prob w/Bogner 101B 20th Ann
I purchased a used but mint 20th 101B not too long ago and the clean (green) channel has developed a "popping" sound. It doesn't start right away it usually takes about 10-15 min to start and it starts out kind of sporatic but then gradually gets faster to where it pops like 2-3 times a second. It's NOT tube related, I have the amp at a local tech (he's not really a tech but he builds his own amps and has done troubleshooting with success for others and he's all I got for being in Puerto Rico) and he hasn't seen anything out of the ordinary. I suggested he turn out the lights and try to observe arching but he says he did it and there is none visible. There is a vid I will try to upload later but just wanted to get some troubleshooting suggestions while he still has it on the bench. Thanks!
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Re: Please Help ID Prob w/Bogner 101B 20th Ann
All my higher gain amps do that at my house. It did not do it where I gig. I found out it was my neighbors electric fence that my home supply was picking up through ground. We turned off his fence momentarily and it disappeared. A power conditioner helped in the end.
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Stevem
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Re: Please Help ID Prob w/Bogner 101B 20th Ann
Since it only takes place on one channel you can rule out the PI and output stage.
I would start off by replacing all of the plate load resistors and cathode bypass caps in that preamp section as this is a cheap and fast way to shot gun that, and any plate load resistors that may have close to 350 volts on the power supply side of them need to 1 watt types, not 1/2 watt types!
What does this amp use for channel switching, relays or Opto couplers?
I would start off by replacing all of the plate load resistors and cathode bypass caps in that preamp section as this is a cheap and fast way to shot gun that, and any plate load resistors that may have close to 350 volts on the power supply side of them need to 1 watt types, not 1/2 watt types!
What does this amp use for channel switching, relays or Opto couplers?
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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: Please Help ID Prob w/Bogner 101B 20th Ann
Thanks for the reply! I'm certain it's not power related due to the fact that it happens at my house where the power is nice and clean and at the tech's place where I'm not sure about the power but it's an entirely different source so the point is I can repeat the results regardless of location.RWood wrote:All my higher gain amps do that at my house. It did not do it where I gig. I found out it was my neighbors electric fence that my home supply was picking up through ground. We turned off his fence momentarily and it disappeared. A power conditioner helped in the end.
¡Despiertate Cerati!
Re: Please Help ID Prob w/Bogner 101B 20th Ann
Thanks for the info! I'll send this to the tech and have him look at the components mentioned. Did you have a look at the vid? The tech thinks it may be one of the black caps in the ckt somewhere because of the nature of the issue (popping) since caps store and release their charge. As far as channel switching I'm not sure but I'll send an email to Bogner and get back to you later on today. Thanks again Steve!Stevem wrote:Since it only takes place on one channel you can rule out the PI and output stage.
I would start off by replacing all of the plate load resistors and cathode bypass caps in that preamp section as this is a cheap and fast way to shot gun that, and any plate load resistors that may have close to 350 volts on the power supply side of them need to 1 watt types, not 1/2 watt types!
What does this amp use for channel switching, relays or Opto couplers?
¡Despiertate Cerati!
Re: Please Help ID Prob w/Bogner 101B 20th Ann
Here's info I got from Jorg @ Bogner today. Any thoughts on this?
Hi Larry,
What is the serial number of the amp? We have never used C-winged Svetlanas in that amp, JJ's. It shouldn't be a problem to bias an amp for a Tech, bias always depends on brand and individual grade of the tubes. With input AC set correct we use a signal generator and scope to bias at min crossover distortion, then set it about 20% lower. Amp has as high as 520VDC B+ so -51 can still be in the range.
We found if there is 4VDC on the 1K/5W resistors that it is an indicator that the tube runs on it's limit, after biasing resetting it so that the voltage is below 4VDC is a good thing to do if you want to e save.
Regarding the popping you describe not sure what that can be, usually tube related but you say it isn't. The flow of the signal is V1/A half triode then it feeds into the EQ circuit via a shielded cable from CS1A to CS1B, after the EQ into the gain and from there into V6 both triodes, boost circuit is in between from there it goes cap C30 to CS2A to CS2B into the volume.
Have him measure the B+ on the V1A and V6A and see if it changes after the popping come in. Maybe it's a leaking coupling capacitor, C26 or C30.
Sorry we do not hand out schematics.
Our amp Tech speaks Spanish if your Tech wants to talk to him, his name is Teodoro, +1 818 765 8929
Regards,
j o r g
Hi Larry,
What is the serial number of the amp? We have never used C-winged Svetlanas in that amp, JJ's. It shouldn't be a problem to bias an amp for a Tech, bias always depends on brand and individual grade of the tubes. With input AC set correct we use a signal generator and scope to bias at min crossover distortion, then set it about 20% lower. Amp has as high as 520VDC B+ so -51 can still be in the range.
We found if there is 4VDC on the 1K/5W resistors that it is an indicator that the tube runs on it's limit, after biasing resetting it so that the voltage is below 4VDC is a good thing to do if you want to e save.
Regarding the popping you describe not sure what that can be, usually tube related but you say it isn't. The flow of the signal is V1/A half triode then it feeds into the EQ circuit via a shielded cable from CS1A to CS1B, after the EQ into the gain and from there into V6 both triodes, boost circuit is in between from there it goes cap C30 to CS2A to CS2B into the volume.
Have him measure the B+ on the V1A and V6A and see if it changes after the popping come in. Maybe it's a leaking coupling capacitor, C26 or C30.
Sorry we do not hand out schematics.
Our amp Tech speaks Spanish if your Tech wants to talk to him, his name is Teodoro, +1 818 765 8929
Regards,
j o r g
¡Despiertate Cerati!
Re: Please Help ID Prob w/Bogner 101B 20th Ann
Bogner support was great when I had a Shiva years ago.
It sounds an awful lot like a cell phone signal, with that steady pulse; but since it's not happening on the other channels maybe not? Could it be that clean channel doesn't have the same amount of heavy shielding and snubbers that the dirty channel had, and hence picks up the cell signal?
Could be a barely cracked solder joint on the board, but I would think the pulse would be more random. Your tech can use either cold spray or small wooden "chopstick" to isolate the area and hopefully the actual part that the faulty connection is made to. At least you know it will be in the clean channel circuitry.
It sounds an awful lot like a cell phone signal, with that steady pulse; but since it's not happening on the other channels maybe not? Could it be that clean channel doesn't have the same amount of heavy shielding and snubbers that the dirty channel had, and hence picks up the cell signal?
Could be a barely cracked solder joint on the board, but I would think the pulse would be more random. Your tech can use either cold spray or small wooden "chopstick" to isolate the area and hopefully the actual part that the faulty connection is made to. At least you know it will be in the clean channel circuitry.