Crack not functioning - guidance requested

[Paul Birkeland]

And when I lift up the left side of the unit, the hum dissipates.

That suggests a loose joint or loose hardware.

[DenverDude]

This is where I am frustrated, Paul. I have resoldered all main terminals 3 times now and I am still getting the same buzz in the (mostly) left and (partially) right channels that I had before I did any resoldering. Obviously me resoldering the main terminals isn't working. I have changed both tubes (with the really expensive Tung-Sol 5998 replacement buzzing even worse than the stock CRC-6080) and to no avail.

I would rather pay you $200+ to determine what I am doing wrong than to suffer every day with frustrating sound because I don't know what to do at this point, even if it takes you 5 minutes to fix/resolve. I have my own expertise where I can fix something in an hour that would take someone who is inexperienced dozens of hours and thousands of dollars to figure out, so I am fine for paying for a seasoned expert to solve the problem. I have tried time and again and it's not doing the job. Plus I am really baffled why the Tung-Sol I purchased is such a dud. Just let me know where I can ship this and how I can pay you. Thanks again.

[diynewbie]

I think Paul is asking you to tighten all the screws attaching the hardware to the aluminum plate.

[Paul Birkeland]

Yes, please be sure all the screws are nice and tight. 

[DenverDude]

Sorry I misunderstood, Paul. I tightened all the hardware down firmly, and although it has helped with the buzzing, after the unit has been operating for 2+ hours, I still am getting noise through the left channel when I tap the table near the unit or tap the unit itself (it's a tinny sound when I tap). And tonight after it being used all day, there is a consistent buzz in both channels. Also the left channel seems to have a tad bit less gain than the right (i.e., there's a very minor balance issue).

It seems like these issues arise once the unit has been used for multiple hours. Any advice?

[Deke609]

It seems like these issues arise once the unit has been used for multiple hours. Any advice?

I have to wonder whether this might be heat related. Do you have the rubber feet installed so that there is at least a 1/4" gap between the wood frame and the table? Are the vent holes on the metal chassis open and clear? I'd also check that the heatsinks are properly and tightly mounted with the supplied mica insulator.

Just some shots in the dark.

cheers, Derek

[DenverDude]

Thanks for the ideas, Derek. The rubber feet were installed to spec, so there is the 1/4 inch gap between the unit and the table. The vent holes are clear  (though I can view a couple of wires when looking inside ... I assume this is normal). The heatsinks are firmly attached too.

To be honest, the unit has always run hot to the touch ... I can keep my fingers on it so it's not as hot as the cylinders on my Triumph when riding for a while, but it's much more than warm.

[Paul Birkeland]

It seems like these issues arise once the unit has been used for multiple hours. Any advice?

Do the voltages change if you leave the amp on for a few hours and recheck them? 

Can you let me know what soldering products you used on the amp?  (solder, flux, etc)

[DenverDude]

Hello Paul -

Here are the measurements as follows:
First reading = Just after turning unit on
Second reading = 6 hours after turning unit on- slight tinny noise in mostly left channel and when I tap on metal base I hear tinny tapping in mostly left channel - unit hot to the touch
Third reading - 2 hours after last reading, unit still on - now low but audible buzz in both channels - when I tap on metal base I still hear tinny tapping in mostly left channel - unit hot to the touch

1 84.3 - 84.2 - 83.4
2 182.8 - 176 - 179.2
3 0 - 0 - 0
4 182.8 - 175.8 - 179.4
5 83 - 83.1 - 82.2
6 0 - 0 - 0
7 112.2 -110.1  - 110.9
8 0 - 0 - 0
9 112.4 - 110.4 - 111.3
10 0 - 0 - 0
11 0 - 0 - 0
12 NA - NA - NA
13 182 - 178.4 - 179.4
14 0 - 0 - 0
15 201.2 - 195 - 198.6
20 0 - 0 - 0
21 220.8 - 214 - 217.9
A1 82.6 - 83.2 - 82.3
A2 0 - 0 - 0
A4 0 - 0 - 0
A5 0 - 0 - 0
A6 83.5 - 83.8 - 83.5
A7 0 - 0 - 0
A9 0 - 0 - 0
B1 83.5 - 83.7 - 83.6
B2 182.2 - 178 - 179
B3 112 - 110.6 - 110.9
B4 82.4 - 82.5 - 82.4
B5 182.2 - 178 - 179.3
B6 112 - 110.8 - 111.2
B7 0 - 0 - 0
B8 0 - 0 - 0

I am using Alphametals 60% tin 40% lead solder with fastacting flux.

Also, since my last soldering job, neither channel plays unless I pull the headphones out slighly and then I can bring the right and left channel in, but it's not perfect.

At this point, I want to send this unit into you to take a look at it. I am at the point where I need help, so let me know where to send in and how you need payment. Thanks for your help...

[Paul Birkeland]

Sure, we can set that up.  It would be helpful to see some build photos before we go down the repair road.

[DenverDude]

Just let me know what you need pics of and I will supply them.

[DenverDude]

Here are several pics of the assembly....

[Paul Birkeland]

OK, you can give Eileen a call on Monday to setup the flat rate repair. 

Thank you for providing the photos, it's helpful to be able to visually confirm that the amp is stock and doesn't have something super obvious going on.