Hi
First post! I have several audio tube amps that, when i power them on, they blow out their fuse. They've all worked fine for some time, and previously I was able to meet with a knowledgable person who did some quick cleaning and adjustment and they worked right away. But they're not working again! what are some quick steps i can do to try to diagnose and/or fix them?
Thanks for any help and advice
-Neal
First post! I have several audio tube amps that, when i power them on, they blow out their fuse. They've all worked fine for some time, and previously I was able to meet with a knowledgable person who did some quick cleaning and adjustment and they worked right away. But they're not working again! what are some quick steps i can do to try to diagnose and/or fix them?
Thanks for any help and advice
-Neal
Have the amps been used regularly? If not, the power supply electrolytic capacitors could have dried out.
Check those parts. You could try reforming the capacitors. Also test the tubes.
When you are sure about the capacitors and tubes, verify the amp fuses are the right size and type.
Then bring the amp up slowly to your line voltage with a FUSED Variac. Don't rely on the fuse in the amp.
If you don't have a Variac, buying one will be cheap compared to replacing damaged parts and tubes.
https://www.parts-express.com/3A-Variac-0-130-VAC-120-840
Check those parts. You could try reforming the capacitors. Also test the tubes.
When you are sure about the capacitors and tubes, verify the amp fuses are the right size and type.
Then bring the amp up slowly to your line voltage with a FUSED Variac. Don't rely on the fuse in the amp.
If you don't have a Variac, buying one will be cheap compared to replacing damaged parts and tubes.
https://www.parts-express.com/3A-Variac-0-130-VAC-120-840
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Many tube amps use a negative grid bias on the output. If a bias adjustment trimmer corrodes so that there is no bias, the output tubes will draw excessive current and blow fuses. Cleaning and adjusting such trimmers will make them work again temporarily. But a long-term solution would be to replace them, preferably with a fixed resistor.
The quick steps demanded by askers are contradictory to their lack of input or any information. So the quicker these steps need to be to solve your issues the more details should be given to knowledgable people wanting to help you for free in their spare time.
My dish washer always worked OK and when it failed someone took a look and fixed something. Today it fails again, what can it be?
Please explain what the fun for us is to have to fight for even a brand and typename? We just don't know the brands/types "all" and "several" and their specifics. How many devices and how many times is this pile of amplifiers powered on per year? What was done last time? You know "some quick cleaning and adjustment" did not fix blown fuses, that is an offense to present here, sorry.
My dish washer always worked OK and when it failed someone took a look and fixed something. Today it fails again, what can it be?
Please explain what the fun for us is to have to fight for even a brand and typename? We just don't know the brands/types "all" and "several" and their specifics. How many devices and how many times is this pile of amplifiers powered on per year? What was done last time? You know "some quick cleaning and adjustment" did not fix blown fuses, that is an offense to present here, sorry.
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You're in great shape today jean paul!! 🤣 🤣 🤣
you just made my day 😁
you just made my day 😁
This is not the right place to talk about it but some time ago I had the idea of creating a thread to give the basics of troubleshooting to newbies.
I have thought about it since and my conclusion is that it is not a good idea.
many people simply come to ask that we solve their problem without trying to understand (I'm not talking about the op that I don't know) and leave with a solution without having learned anything other than ... the solution.
I find that it contributes greatly to the decline in the level of general knowledge and I realize it every day because I still work in troubleshooting and I am confronted with breakdowns so ridiculous that I want to yell at the people to wake them up (like dead RF thermostat batteries) and when I explain to them, I often have the impression of having made them discover the fire or the wheel.
I am not surprised that many charlatans succeed on youtube and the worst is that "the more the master is stupid, the more the dog is faithful".
I may be going to open a thread in the living room to talk about it but I also think that with the differences in culture gathered here, it will quickly turn into something big, suddenly, I don't know...
I have thought about it since and my conclusion is that it is not a good idea.
many people simply come to ask that we solve their problem without trying to understand (I'm not talking about the op that I don't know) and leave with a solution without having learned anything other than ... the solution.
I find that it contributes greatly to the decline in the level of general knowledge and I realize it every day because I still work in troubleshooting and I am confronted with breakdowns so ridiculous that I want to yell at the people to wake them up (like dead RF thermostat batteries) and when I explain to them, I often have the impression of having made them discover the fire or the wheel.
I am not surprised that many charlatans succeed on youtube and the worst is that "the more the master is stupid, the more the dog is faithful".
I may be going to open a thread in the living room to talk about it but I also think that with the differences in culture gathered here, it will quickly turn into something big, suddenly, I don't know...
Hi - Here's the models :
I had connected the Pilot to the ST70, and separately the A300, and these worked well until about a couple of years ago. Haven't been able to get the Mark III's running, got them similarly couple years ago.
Apologies for my ignorance and not providing this information - I am a complete beginner, in awe of the sound of these when they run, and grateful for any help or advice. I hope to learn and get these running again, and I'll get a Variac like @rayma mentioned (I found a similar one up to 5A freeship on Amazon), and I'm guessing I'll need a supply of fuses since they might blow out a couple times until I fix them?
In terms of checking, I guess I can try cleaning the sockets and reseating the tubes, and changing the bias using a multimeter?
I'd be happy to post what kinds of further information would be useful to know?
Thanks very much
-Neal
- Pilot 590 Tuner Preamp
- Harman A300 Integrated
- Dynaco ST70
- 2x Dyna Mark III
I had connected the Pilot to the ST70, and separately the A300, and these worked well until about a couple of years ago. Haven't been able to get the Mark III's running, got them similarly couple years ago.
Apologies for my ignorance and not providing this information - I am a complete beginner, in awe of the sound of these when they run, and grateful for any help or advice. I hope to learn and get these running again, and I'll get a Variac like @rayma mentioned (I found a similar one up to 5A freeship on Amazon), and I'm guessing I'll need a supply of fuses since they might blow out a couple times until I fix them?
In terms of checking, I guess I can try cleaning the sockets and reseating the tubes, and changing the bias using a multimeter?
I'd be happy to post what kinds of further information would be useful to know?
Thanks very much
-Neal
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Ok, please choose only one amplifier to start working with.
Don't try to repair more than one at a time.
That will be hopelessly confusing for everyone.
Please list the rest equipment that you have at hand now.
Also, do you have any spare tubes?
Don't try to repair more than one at a time.
That will be hopelessly confusing for everyone.
Please list the rest equipment that you have at hand now.
Also, do you have any spare tubes?
OK since I'd like to hear some music asap I'll start with the A300!
I have a couple of multimeters, probably a soldering iron, some general old tools like wire strippers, a breadboard. I don't know how to check a capacitor or have any other special equipment. Also its fuse says BUSS AGC 3 250V so I should probably get more of those?
Thanks!
I have a couple of multimeters, probably a soldering iron, some general old tools like wire strippers, a breadboard. I don't know how to check a capacitor or have any other special equipment. Also its fuse says BUSS AGC 3 250V so I should probably get more of those?
Thanks!
Here is the schematic for reference. It's very straightforward.
Post good photos of inside the unit, top and bottom.
Also post a photo of your soldering iron. Are those digital voltmeters?
If you have to order the parts, hold off on the fuses for a bit.
Post good photos of inside the unit, top and bottom.
Also post a photo of your soldering iron. Are those digital voltmeters?
If you have to order the parts, hold off on the fuses for a bit.
If the fuse blows instantly, suspect shorted transformer, diode rectifiers or filter capacitors, or some other short on the B+. If it takes a while, it could be coupling capacitors, or a gassy output tube.
That's good, I know the A300 very well, I have three and a fourth from EJ.Korvette.
Great device and very simple, impossible or almost impossible to break down without human intervention.
Great device and very simple, impossible or almost impossible to break down without human intervention.
We really, really should start a sticky thread about restoration of Golden Age audio gear. The same questions come up regularly, and the same basic solutions apply, but it's spread out over so many threads with search-unfriendly names that folk new to diyAudio have to start fresh every time.
The needed topics would include safety issues (of various kinds), operation at modern line voltages, minimum test gear including home-made (lamps), sources for parts, rounding up the usual suspects, possible modifications to accommodate modern valve production, etc.
Anyone want to begin?
All good fortune,
Chris
The needed topics would include safety issues (of various kinds), operation at modern line voltages, minimum test gear including home-made (lamps), sources for parts, rounding up the usual suspects, possible modifications to accommodate modern valve production, etc.
Anyone want to begin?
All good fortune,
Chris
That's a very good idea, but a huge topic.
Maybe start with a list of the best and worst candidates.
Maybe start with a list of the best and worst candidates.
I don't like folk having a go at beginners for their lack of knowledge, we all started out knowing nowt, be gentle. The OP aked a question, he's willing to learn, this forum is there to share knowledge, ridicule doesn't help.
First off DO NOT POWER ANYTHING UP AGAIN .If a fuse blows straight away that points to a gross fault. For a beginner with little or no knowledge the best thing he/she can do is to take it to a competent repair tech, if you don't there's a change you can do even more damage resulting in making the issue worse.
That said there is something you can do with no equipment or knowledge, that's too open the device up and look for anything that looks wrong, EG wires loose, burnt/scorched components or leaky gunk.
Without a meter or any test gear the next best thing you can do is post some very good quality pictures here, we might spot something.
The next step would be to build yourself a lamp limiter and a half decent DMM (digital multi meter) Regards, Andy.
First off DO NOT POWER ANYTHING UP AGAIN .If a fuse blows straight away that points to a gross fault. For a beginner with little or no knowledge the best thing he/she can do is to take it to a competent repair tech, if you don't there's a change you can do even more damage resulting in making the issue worse.
That said there is something you can do with no equipment or knowledge, that's too open the device up and look for anything that looks wrong, EG wires loose, burnt/scorched components or leaky gunk.
Without a meter or any test gear the next best thing you can do is post some very good quality pictures here, we might spot something.
The next step would be to build yourself a lamp limiter and a half decent DMM (digital multi meter) Regards, Andy.
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Apparently, this so-called "knowledgable person" isn't so knowledgable.
(maybe a 14 year old kid with a golden screwdriver?)
Because if they had ANY insight or experience into such equipment, they'd have been able to troubleshoot for potential issues.
Wouldn't it make sense to remove all of the tubes, replace the fuse, and power it up? (cut in half troubleshooting)