[mikeymad]

I just picked up a regular 5w 100ohm ceramic resistor (just like what is in there).

Cheers,

 

[mikeymad]

Well for $1.50 I have found out that there is something else going wrong.

I replaced the Resistor:

It was holding it's 100ohm rating. I powered it all up again. The low voltage side was still working as before. But the high voltage was reading OF (which is overrange) which means that it should have had a lot of voltage. But I was not sure at the time. I unplugged everything and then started to check various resistors and connections. Well when I checked the 450V connection again it gave a spark (I guess releasing the Cap storage). Well once that happened it turns out that burnt out the resistor in question again. So, I guess that I should have bought two. But the main thing is that there may be another issue going on. This may require some more research.

Cheers,

 

[twoears&oneheart]

soon, mikeymad would be skilled enough to give us a

in-house mikeymad brand of balanced tubed transformer tripled amp...

 

[nikongod]

ACK!!!111 PLEASE be supercareful working with HV.

If there is residual voltage on a circuit, aside from being potentially lethal, it may not allow for the proper measuring of resistance.

 

[braillediver]

The resistor failing is a symptom of the cause not the cause. I would do some more looking before replacing the resistor and powering it up again.

As it is now the resistor is being used as a fuse and other things might fail because of stress- will the resistor fail first or something else in the circuit.

You’ll probably have to lift / remove the PCB and look at the bottom for signs of heat etc. Then you can follow the circuit.

Have you been able to contact Mikhail? If you tell him the part number etc he should be able to suggest things to check to isolate the problem. He knows the circuit.


Good luck and be careful. Potentially dangerous but not more so than most things.

Mitch

 

[takezo]

please be careful.
if you haven't, it may be safer to use alligator-type grip on one of
the voltmeter leads so that you don't have to use both hands...
using just one hand will prevent you from becoming part of the
circuit and accidents...

and braillediver is right, you should stop at this point and contact
mikhail for directions. he's probably seen this problem many times
before.

 

[mikeymad]

Thanks for the advise (and concern) everyone. And I took it to heart. I was away this weekend. But I was able to go pick up a new resistor today.

My plan was to replace the dead one, measure everything, hook up everything including the tubes and then turn it on.

So I replaced the resistor, just as above. All the resistors measured out as rated. I put the case back together. I hooked up the PSU and amp and put in a cheap set of tubes.

Turned on the power, and hey we have power.

The Glow is back.......

I hooked it up to my DAC from my computer. And first sound was only static... much like white noise. Well after a system reboot, and making sure the DAC was woking on the WA6. I hooked it all back up... and.... music in the house again from the ES-1 and 4070's!!!!

It sounded alright... After a bit I was hearing a little crackling from the 4070's. So I powered it down swapped out the tubes with some others I had, and then powered it back on and re-set the bias.

I seem to be pretty much back to normal. I will run it this way for a couple of days, and then swap to my high end tubes and reset the bias again.

Crossed fingers.....

Cheers,

 

[mikeymad]

Post reply: there does seem to be some micro-phonics coming from the left channel, so I am not saying everything is fine at this point. Just up and running.

 

[neilvg]

It's great you were able to troubleshoot most of this yourself. However, too bad you could not make it to the meet with your amp. Mikhail showed up and I'm sure he would have taken a looksey.

Neil

 

[mikeymad]

I know I was bummed (and glad for everyone else) to see that he showed up (and I missed him).

I am glad that I have a running amp at this point, It may take some time to figure out the other issues I have going on. Still may have to send it back at some point, but not yet.....

Cheers,

 

[Hirsch]

Just because the amp works now does not mean that it will keep working. Something blew that resistor. The odds are that you've got a bad capacitor. It's likely one of the big Nichicon's. Do follow up on the advice that you've been given and contact Mikhail.

You do realize that by doing this yourself, and continuing to use the amp with possible damaged parts, Mikhail no longer has any warranty obligation to you if whatever damaged that resistor goes on to damage something else in your amp? DIY repairs are tempting, but if done without the manufacturer's express authorization, any damage caused by a poor or incomplete repair is not covered under any warranty. If there is any chance at all that your amp still has issues, I'd get them fixed right, and for free, rather than risk a big repair bill by playing around with it.

It's possible that Mikhail may help you do the repair yourself, and may send parts, if he chooses to do so. He might also want to look at the amp himself, in which case you have to send it to him. But until he's involved in the repair, you've got no warranty if it backfires.

 

[mikeymad]

Fully Agree Hirsch.... but then again there is no way to know if any amp out there will be working tomorrow.

So rather than ship mine off for 6 months to a year, I learned more about amps and what makes them work. Took my time and measured every component that was in the amp and PSU, and found a bad part. Why it went out? I have no idea. Sometimes I don't know why a part on my car goes bad, I just replace it when it does. Now why did the resistor that I put in go out? I think that I shorted out the connection and discharged all the Caps through it. my bad. Now that I have replaced it. I have power and sound. And after lot more testing parts and looking at the amp. It looks like one of the small caps was resting against the volume control. And this was making noise.

So I pulled it away a bit, and I seem to have eliminated pretty much any issues that I have with the amp. I have a little microphonics thing going on. But I have not gone back to my high end tube set yet. So I am reserving judgement until then.

Did I void any warranty? You Bet. Did I know that when I opened it up? you bet. Do I mind? Not that much.....

There was no real way that I was going to give up my amp for 6 months to a year. It was never going to happen. If I have to replace most of the Caps, and resistors in this thing, I would. I spent $1.50 x 2 for a couple of resistors, and a hand full of hours playing with a nice amp. I learned a lot, and that was a part of the fun for me. I have to give a lot of thanks to the Cary Tech line, for putting it in my mind that I could figure out what was wrong, and probably repair it (300SEI that was). Am I an amp designer or an EE? Nope. But then again I can't make a car, but I can find out that is wrong and replace a part.

Now I am not one to have anyone open up their amps. This was just me doing what I do. And hey, if I do have to send in my amp for some reason, then I will pay for it. No problem with that.

But for now I have Harry Connick kicking it hard, and I am happy....

Cheers,

 

[mikeymad]

Update:

Been listening for every single artifact over last few days. Alwasy thinking, is that on the recording? Is it the headphones, or is there something going on with the amp again....

I switched over to very well known recordings last night, and I heard nothing but music from my 4070's for 5 hours.

So I think I will be swapping out for the good tubes and heading to the O2 next. Making sure to reset the bias.

Cheers,

 

[jamato8]

I have always, in the end, gone a head and fixed my own gear even if warranty unless something too small like the dac going out in a portable amp. Those are just too much work even though I have built dacs.

Anyway, I love to work on equipment and there is no better way to take the mystery out of what is going on and optimizing what you have.

On the Black Gates, they have been found to be even better if the shrink is taken off of them and then wrapped in teflon tape (tight). This decreases resonances. Some people even prefer just having the BG's naked as you don't have the dielectric effect of the so-so wrap they use. Also even in areas that metal oxide resistors "can" be used I will always go with a good Kiwame or Mills. Everything is in the signal path.

On your attenuator it sure would be interesting to sub some nice resistors for the most used on the attenuator. I like Dale resistors and they are a great bang for the buck, or pennies, but in the end there are better. I would go with Kiwame for the noninductive and transparent quality.