[tries_new_things]

After 5 months of use, one of my Cymbals stopped working. No sound. LED stays red.

I pulled the cover and found resistors R1 and R3 (3 watt 330 ohms connected in parallel) had gotten hot enough to cause localized burning of the circuit board and partially oxidize the wire leads. My other Cymbal shows similar overheating though not to the same extent.

Maybe I got a batch of resistors with inadequate ability to dissipate heat?

I'm considering replacing them with a pair of 82W-5-ND (DigiKey) connected in series. I'm thinking a series pair might provide a little more stable heat dissipation scenario in the event the resistances don't match exactly. I guess I would just connect the resistors directly to the choke lead on one end and the transformer tap on the other.

A few questions.
The proposed resistors are the wirewound type. Would this be an issue?
Aside from giving each board a good inspection, are there other locations I should check for trouble? I did verify that R4 is the indicated 220kOhm value.

[harryf]

That's a very good idea.I'm rebuilding my cymbal and i'm going to use higher rated wirewound's.A guy also once told me that the cymbal's can overheat/run hot.I would think wirewound's would fix that.
In my case the overheating was from a stupid mistake of my own but i figure why not add insurance.

[poty]

I think you should check the consumption current first. It is mention on the scheme. You can measure the voltage drop on the R1+R3 (according to the easy counting it should be around 25V). So the wattage should be around 4W which is 1.5 times less than the nominal value of the resistors (3+3=6W) - they should not be hot.
If you have more than 25V on the R1+R3 you should check what circuit get more current than nesessary. There is some currents mentioned on the scheme. Sometimes it could be calculated. I think you have electrolytic capacitors leakage, or something wrong with output transformer. But it could be wrong balance, bad tube or too big load.

[tries_new_things]

Thanks poty, will try. I'll be out for a couple weeks.

[Yoda]

Generally, Jim H seems to design conservatively within operating limits of the spec'd components.  I would think if your burning things out, then a component is out of order or your assembly is off. 

Maybe one thing to check is how the output xformer is configured for your outputs vs the nominal impedance of your speakers.   I kind of doubt this would throw off internals so much, but rather just optimize the sound.  Impedance dips over freq. range are something to watch out for.

If you've ever run a signal in the amp without a load on the outputs, or your speaker cables get loose, you run the risk of frying the transformer.

Matt

[hagtech]

Likely one of the output tubes went bad (short).  This will pull a lot of B+ current, but possibly not enough to trip fuse.  Check them all before powering up again.

jh

[tries_new_things]

Likely one of the output tubes went bad (short).  This will pull a lot of B+ current, but possibly not enough to trip fuse.  Check them all before powering up again.

jh

Yeppers. This was it. Thank you.

[tries_new_things]

Replacing the tube (6H30) worked, and the pair of Cymbals have run beautifully till now. Repeat of problem. One of the power tubes, with additional heating of R1 and R3. Replacing the tube fixes it completely.

A couple of questions...

Might I have gotten a batch of tubes more likely than average to fail this way?
How feasible might it be to add a separate fuse to protect this particular part of the circuit?

[hagtech]

Yes, looking back at the design I should have probably incorporated a fuse in the B+ line to protect against bad tubes.  It seems there are many 6H30 tubes that fail in this manner. 

jh

[tries_new_things]

I can imagine how I might mod this. What might a recommended fuse be?

[analog97]

Ya know, I have been a Hagerman fan for years.  I now can not find the Hagerman forum.  I tried multiple searches and failed.  Can anyone tell me what has happened?

Thanks in advance. 

[hagtech]

Forum is going to disappear.  Skyrocketing costs beyond my budget.

jh

[JohnR]

Sorry Jim, but a 33% increase in 5 years is not exactly "skyrocketing costs." I realize that it would of course be better for you if I continued to work for free or less, but I'm afraid that I simply can't do that anymore. If $33 per month is out of your budget, OK, but please don't insult me with crap about "skyrocketing costs."

Thanks

[analog97]

The exclusion of a Hagtech Forum will result in losses to far more folks than any gain to a single person.  My request is to step back from the ledge and meet in the middle.  Respectfully requested by a "loser".

[hagtech]

Ok.  Let me take that into consideration...

jh

[poty]

Sorry Jim, but a 33% increase in 5 years is not exactly "skyrocketing costs." I realize that it would of course be better for you if I continued to work for free or less, but I'm afraid that I simply can't do that anymore. If $33 per month is out of your budget, OK, but please don't insult me with crap about "skyrocketing costs."

Is it possible to explain several days of downtime just in the sake of slightly different design (and many victorious reports way before the transition has been done successfuly on the first page of the site)? Now, I've lost my "read" status for all topics of the circle which is not good at all either.