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[Francis Dong]

Hello everybody. I've got a Situation that I'm trying to find help concerning y buddy's bass head. There is a constant rattle when the head is on. When we opened it, it turned out thetube was rattling. After securing the tube with foam and tape we wentfor another run, the rattle was gone for the most part but the fan was still very audible. Is this normal? Also in the last gig, the head started making very audible noise. It seems like everything is going wrong with this head and it's supremely frustrating. I don't know much about internal electronics so that is just perplexig things. Has anyone else run into a similar issue and have an explanation and or solution? The tubes seem to be functioning fine.

[Charlie Zureki]

Francis Dong wrote on Fri, 12 March 2010 18:41

Hello everybody. I've got a Situation that I'm trying to find help concerning y buddy's bass head. There is a constant rattle when the head is on. When we opened it, it turned out thetube was rattling. After securing the tube with foam and tape we wentfor another run, the rattle was gone for the most part but the fan was still very audible. Is this normal? Also in the last gig, the head started making very audible noise. It seems like everything is going wrong with this head and it's supremely frustrating. I don't know much about internal electronics so that is just perplexig things. Has anyone else run into a similar issue and have an explanation and or solution? The tubes seem to be functioning fine.

 How old is this amp head? Parts tend to loosen when subjected to low end vibrations from sitting on a bass cabinet.  Open the amp, and check all components to see if they "rattle".  Re- seat all of the tubes?

 When tube head components start to fail... they all seem to start failing. Have you ever changed out any tubes? If not, break down and purchase some tubes.  
 

 Fan bearings wear out over time. Check the blades to see if they're hitting the fan housing. It may be time to replace the fan.

 What do you mean by "the head started making an audible noise?"
Are the tubes squealing?

 When transporting Tube amps, they should be handled like fine crystal...free from bumping, dropping, or other rough handling.

Hammer

 

[Francis Dong]

Thanks for responding hammer.
The type of noise I am talking about is the sound of a disconnected chain. Say like you unplug the TRS from your guitar when it is still plugged into your amp, and then touch it to something metal or your body.  The noise is consistent and does not diminish over time.
I'm not sure how old the unit is because my friend bought it off someone else.  
We are going to dust the fan and see if that solves the fan problem, if not replace it.
I am also going to try new tubes.
I want to replace the seating but am unsure of how to do it/scared of permanently damaging the amp.  Is there a place/website/forum that has tutorials for this type of thing?

[Art Welter]

The SVT-3PRO has  three 12AX7 preamp tubes, one 12AX7 and one 12AU7
driver tubes and a transister power amp section, so fortunately the tubes are not very expensive.

I would doubt they all would go bad, but if they have gone microphonic, replace them.

What do you mean, “replace the seating”?

[Ned Ward]

Ampeg moved production overseas to Vietnam I believe about 3 year ago and may have had some QC issues  - enough that they're moving some production back to the US. How much of that is reaction to QC and how much is marketing to charge a premium I don't know, but I'd google your buddy's amp to see if there's problems besides microphonic tubes.

A quick search of the Talkbass forums yielded this discussion:
http://www.talkbass.com/forum/showthread.php?t=142861


JJ tubes are strong, not microphonic and relatively cheap. Or your friend can call Mike K at kcanostubes.com and get some good stuff - Mike's great to deal with  and happy to recommend new or NOS tubes based on tone goals and your budget.

I've seen these on eBay; no idea if they work as claimed or are snake oil, but for $9, who knows.

http://cgi.ebay.com/TUBE-AMP-PREAMP-DAMPERS-FOR-12AX7-12AU7- ECC83-EL84-6922_W0QQitemZ370343758933QQcmdZViewItemQQptZVint age_Electronics_R2?hash=item563a354c55#ht_4208wt_1167