Topic: Amp's right channel is not balanced with the left.

[ATJr.]

This is the second amp that he designed and built that I am fixing, both are PP amp one is KT88 and this one is 6550.

does he have a name?, i think you should name him, otherwise all guys that are into diy will become suspects....

as a matter of courtesy, the one who built the amp should have the first crack at repairing the amp, after all selling amps comes with an after sales service, it goes without saying.....

if it were me, i would not touch it until the maker of that amp has been suffieciently informed and given the chance to work on the repairs...this is how it was in the old days, shouldn't be any different today....

owner's of tube amps must realize that having one is not like having an SS amp. owners are obliged to know more about their amps unlike SS ones...

[qguy]

Having a tube amp is like getting a vintage car, it requires some TLC.. unlike an SS amp..

This was my advise to a friend who dove into the tube amp headfirst, specially if your going to go the DIY route or the used / Vintage market route..

owner's of tube amps must realize that having one is not like having an SS amp. owners are obliged to know more about their amps unlike SS ones...

[supotman]

Having a tube amp is like getting a vintage car, it requires some TLC.. unlike an SS amp..

This was my advise to a friend who dove into the tube amp headfirst, specially if your going to go the DIY route or the used / Vintage market route..

...meaning SS amp is modern tech

[ATJr.]

...meaning SS amp is modern tech

tubes were invented in 1903 by Lee DeForest, he invented the triode, the transistor was invented in 1946 at Bell Labs. so that makes SS the newer technology.....

[praktikal]

tubes were invented in 1903 by Lee DeForest, he invented the triode, the transistor was invented in 1946 at Bell Labs. so that makes SS the newer technology.....

43 years gap. matanda pa sa akin ang pagitan.

informative! tnx

[Bogsle]

owner's of tube amps must realize that having one is not like having an SS amp. owners are obliged to know more about their amps unlike SS ones...

Having the tube amp exprience for sometime now, I could not agree more.

It's kinda hard nga lang for us who don't have the background nor the schooling, coz we have to really catch up and learn as much as we can, in my opinion. But nevertheless necessary.

[Bogsle]

This is the second amp that he designed and built that I am fixing, both are PP amp one is KT88 and this one is 6550.

does he have a name?, i think you should name him, otherwise all guys that are into diy will become suspects....

yeah, since it was brought up here, could you give us a name please?

[ATJr.]

It's kinda hard nga lang for us who don't have the background nor the schooling, coz we have to really catch up and learn as much as we can, in my opinion. But nevertheless necessary.

if you paid carefull attention to your physics class in high school and in college, uderstanding tubes should not be that hard.....

and these days, we have the internet and you can find anything you want to know with just a few mouse clicks and keyboard typing....

i am of the belief that the tube art should not be lost, it is up to the younger generation to pick up, as we are no longer young, and in a few years will be gone......

[4krow]

  Soory, I am not very good with computor websites, so I'm not sure where to post this question. I recently bought a used Cayin A70-T off of e'bay, and have loved it. Now the bad news...today the amp just quit working. no blown fuse, no bad conn. at the power cord iec conn, no bad rectifier tube! I tried these things one at a time, and no good. I did wonder if all the tubes need to be plugged in, as I only had the rectifier tube plugged in when I swapped to another tube. I did take the bottom cover off, just to look and see very impressive work inside. Nothing appeared to be burnt or loose. Now if I can find a place to buy a service manual, then there is a tech nearby that would be able to at least trouble shoot this problem. So, is there any place that I can get ahold of a service manual?

         Thx in advance,  Greg

[qguy]

1. Which version of the A-70T did you get.  Is it the Autobias model with the switch to changed from Kt88 to El34 ?, if not you would need to changed the BIAS if you swap tubes otherwise something can go wrong...

2. What tubes were there initially ?

3. what tubes did you put in ?

4. Don't tell me you swapped tubes w/o turning it off ?

   I did wonder if all the tubes need to be plugged in, as I only had the rectifier tube plugged in when I swapped to another tube

 

[4krow]

  Thx for your response. what I meant was that I took the tubes out of the amp before turning it over to remove the bottom cover. Then I only put the new rectifier tube back in to see if the amp would work. Nothing happened. But I wonder if all the tubes need to be plugged in in order to light the power indicator(actually, I doubt it, but just wanted to make sure). So, at this point, a service manual is the best step for a tech to trouble shoot this problem. I was just hoping there might a simple fix for the problem before getting too involved in an 'autopsy'.
                       thx again, Greg

[Adam Warlock]

  Thx for your response. what I meant was that I took the tubes out of the amp before turning it over to remove the bottom cover. Then I only put the new rectifier tube back in to see if the amp would work. Nothing happened. But I wonder if all the tubes need to be plugged in in order to light the power indicator(actually, I doubt it, but just wanted to make sure). So, at this point, a service manual is the best step for a tech to trouble shoot this problem. I was just hoping there might a simple fix for the problem before getting too involved in an 'autopsy'.
                       thx again, Greg

You mean you turn on the amp with the rectifier tube only? If your A70T is not autobias, All the tubes should be back in there original place before you turn it on.
If all the tubes where back in thier original place and you replaced the old rectifier tube with the new tube, maybe the new rectifier tube is busted.

Cheers

[4krow]

  Thanks for the suggestion. Even as I tried it, there was still no power. The day that it happened, i.e. when the amp died, there was a failure in the city power system. The electrical system tried to reset itself 4 four times before it came back up for good. I can only imagine how many other devices in town that were affected! So, it seems that after tying these different simple tests, it may well be time to take the A70 in for service. A service manual would be very helpful to the tech, and I wish I could find one available.  Any suggestions?   Greg

[qguy]

I would assume its the power supply... Check if theres a busted fuse, any competent tech with experience in repairing tubes should be able to fix the problem.

You can try to get in touch with Audio Amplified or your nearest Cayin Dealer in your area

[4krow]

 I have left a message for Steve at VAS here in the US, and hopefully he will be able to get a service manual for me. And yes, I agree, it is the power supply that I suspect most. The fuse is good, the rectifier tube is fine, and the ac conn is good to the amp., so next, we will have to 'go inside'. I'll keep you posted, and thx!   Greg

[ATJr.]

  Soory, I am not very good with computor websites, so I'm not sure where to post this question. I recently bought a used Cayin A70-T off of e'bay, and have loved it. Now the bad news...today the amp just quit working. no blown fuse, no bad conn. at the power cord iec conn, no bad rectifier tube! I tried these things one at a time, and no good. I did wonder if all the tubes need to be plugged in, as I only had the rectifier tube plugged in when I swapped to another tube. I did take the bottom cover off, just to look and see very impressive work inside. Nothing appeared to be burnt or loose. Now if I can find a place to buy a service manual, then there is a tech nearby that would be able to at least trouble shoot this problem. So, is there any place that I can get ahold of a service manual?

         Thx in advance,  Greg

Hi Greg,

you can try replacing the power cord if that is the detachable type, maybe it was dislodged when you turned it over, else try a different outlet....

[qguy]

different outlet in a different room.. it could be the circuit breaker.. or at least try to plug something else in the same outlet and check it that equipment works

Hi Greg,

you can try replacing the power cord if that is the detachable type, maybe it was dislodged when you turned it over, else try a different outlet....

[ATJr.]

different outlet in a different room.. it could be the circuit breaker.. or at least try to plug something else in the same outlet and check it that equipment works

yeah, good idea....

[4krow]

  WELL, I FOUND THE PROBLEM! Not exactly where I would have searched first. There was a defective connection in the fuse receptacle, and I recrimped it. Now the problem is fixed. Who ever would of thought...but thanks to a good vom, and a step by step approach to the problem, the reoccuring test result from the EIC socket led me to investigate what looked to be a perfectly connected fuse holder. Anyway, what a relief. Can you imagine the cost of time and shipping for such a small problem? Well guys, back to the 'musyc', and thanks to all for the support! One note for future reference; the power indicator will light on this unit even if there are no tubes plugged in(even the rectifier tube).         cheers, Greg

[ATJr.]

were you using quick connects and does the fuse have spades? good job!

[4krow]

  Thx!     Thats just it, all conn were factory soldered, no quick conn. And the fuse is just the regular type cylinder shape. No spades, just the fuse holder was not making contact with the crimped conn from the factory part. This part is defective from the supplier, not done by Cayin themselves. I just feel lucky....now, back to the musyc.....Greg