Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to rec.antiques.radio+phono,sci.electronics.repair
|
|||
|
|||
Carvin X50B tube amp
Amp seems to work perfectly well, being repaired for minor problem, no
succeptibility to microphony or tinging distortion. Testing the 2x EL34, gains are good and matched but after a minute on heated C/H insulation check, the resistance gradually decreases to 1M for one and 0.5M for the other. What problems will this lead to if continued use, and how quickly ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#2
Posted to rec.antiques.radio+phono,sci.electronics.repair
|
|||
|
|||
Carvin X50B tube amp
On Feb 25, 7:33*am, "N Cook" wrote:
Amp seems to work perfectly well, being repaired for minor problem, no succeptibility to microphony or tinging distortion. *Testing the 2x EL34, gains are good and matched but after a minute on heated C/H insulation check, the resistance gradually decreases to 1M for one and 0.5M for the other. What problems will this lead to if continued use, and how quickly ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list onhttp://home..graffiti.net/diverse:graffiti.net/ It means that the tubes are not precisely matched. Sadly, "matching" tubes these days is typically based only on "gain" and done for a quick claim to inflate prices. No problems if each tube has an individual bias adjustment, and you watch over it. Even if they are biased together and that bias is attended-to, there should be no problems. How many hours on these tubes and are they driven to extremes or not? What are you testing with? http://hereford.ampr.org/Tube4.php?tube=6CA7 Peter Wieck Wyncote, PA |
#3
Posted to rec.antiques.radio+phono,sci.electronics.repair
|
|||
|
|||
Carvin X50B tube amp
Peter Wieck wrote in message
... On Feb 25, 7:33 am, "N Cook" wrote: Amp seems to work perfectly well, being repaired for minor problem, no succeptibility to microphony or tinging distortion. Testing the 2x EL34, gains are good and matched but after a minute on heated C/H insulation check, the resistance gradually decreases to 1M for one and 0.5M for the other. What problems will this lead to if continued use, and how quickly ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list onhttp://home.graffiti.net/diverse:graffiti.net/ It means that the tubes are not precisely matched. Sadly, "matching" tubes these days is typically based only on "gain" and done for a quick claim to inflate prices. No problems if each tube has an individual bias adjustment, and you watch over it. Even if they are biased together and that bias is attended-to, there should be no problems. How many hours on these tubes and are they driven to extremes or not? What are you testing with? http://hereford.ampr.org/Tube4.php?tube=6CA7 Peter Wieck Wyncote, PA Unknown age, matched GT tubes, no date on tubes used by a pub rock band tested on Avo CT160 |
#4
Posted to rec.antiques.radio+phono,sci.electronics.repair
|
|||
|
|||
Carvin X50B tube amp
On Feb 25, 9:38*am, "N Cook" wrote:
Unknown age, matched GT tubes, no date on tubes used by a pub rock band tested on Avo CT160 OK... Attend to the bias to the extent possible, and suggest that they travel with a spare set of tubes. If you have a new 6CA7/EL34 to test against, try that just to make sure you are not too far off. At least you are using one of the very few testers that actually gives reliable information. Peter Wieck Wyncote, PA |
#5
Posted to rec.antiques.radio+phono,sci.electronics.repair
|
|||
|
|||
Carvin X50B tube amp
Peter Wieck wrote in message
... On Feb 25, 9:38 am, "N Cook" wrote: Unknown age, matched GT tubes, no date on tubes used by a pub rock band tested on Avo CT160 OK... Attend to the bias to the extent possible, and suggest that they travel with a spare set of tubes. If you have a new 6CA7/EL34 to test against, try that just to make sure you are not too far off. At least you are using one of the very few testers that actually gives reliable information. Peter Wieck Wyncote, PA This one was used by REME Wing Hebrides in 1984 |
#6
Posted to rec.antiques.radio+phono,sci.electronics.repair
|
|||
|
|||
Carvin X50B tube amp
RF wrote in message
... Peter Wieck wrote: On Feb 25, 7:33 am, "N Cook" wrote: Amp seems to work perfectly well, being repaired for minor problem, no succeptibility to microphony or tinging distortion. Testing the 2x EL34, gains are good and matched but after a minute on heated C/H insulation check, the resistance gradually decreases to 1M for one and 0.5M for the other. What problems will this lead to if continued use, and how quickly ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list onhttp://home.graffiti.net/diverse:graffiti.net/ It means that the tubes are not precisely matched. Sadly, "matching" tubes these days is typically based only on "gain" and done for a quick claim to inflate prices. No problems if each tube has an individual bias adjustment, and you watch over it. Even if they are biased together and that bias is attended-to, there should be no problems. How many hours on these tubes and are they driven to extremes or not? What are you testing with? http://hereford.ampr.org/Tube4.php?tube=6CA7 Peter Wieck Wyncote, PA Huh, he is talking about heater to cathode leakage. Nothing to do with matching the tubes. The amount of leakage you have is no big deal for power tubes, if it gets below 100K then have a hum problem. That was the sort of info I was after. I was wondering if there could be some sort of thermal runaway situation. I'd not noticed any hum but will make a point of trying to measure it for later reference purposes. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#7
Posted to rec.antiques.radio+phono,sci.electronics.repair
|
|||
|
|||
Carvin X50B tube amp
RF wrote in message
... Peter Wieck wrote: On Feb 25, 7:33 am, "N Cook" wrote: Amp seems to work perfectly well, being repaired for minor problem, no succeptibility to microphony or tinging distortion. Testing the 2x EL34, gains are good and matched but after a minute on heated C/H insulation check, the resistance gradually decreases to 1M for one and 0.5M for the other. What problems will this lead to if continued use, and how quickly ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list onhttp://home.graffiti.net/diverse:graffiti.net/ It means that the tubes are not precisely matched. Sadly, "matching" tubes these days is typically based only on "gain" and done for a quick claim to inflate prices. No problems if each tube has an individual bias adjustment, and you watch over it. Even if they are biased together and that bias is attended-to, there should be no problems. How many hours on these tubes and are they driven to extremes or not? What are you testing with? http://hereford.ampr.org/Tube4.php?tube=6CA7 Peter Wieck Wyncote, PA Huh, he is talking about heater to cathode leakage. Nothing to do with matching the tubes. The amount of leakage you have is no big deal for power tubes, if it gets below 100K then have a hum problem. Measured no more than 1mV rms hum over 4 ohm output for this one , level set for 2.25 W of 400Hz output, but disconnected and monitoring for shorted input -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Carvin Pro Bass 100 combo | Electronics Repair | |||
CRT tube - Releasing vacuum for tube removal/disposal | Electronics Repair | |||
36 inch Samsung TSF-3579 tube TV - Size and Weight of Picture Tube | Home Repair | |||
WTD: Schematic/Svc Manual for Carvin MX601/MX641 | Electronics Repair | |||
"TUBE GUYS" - Found this Pocket tube Tester In the Rafters - Please comment | Electronics Repair |