Peavey Tour 700 Buzzing

[Modman]

Hey everyone,

I had a gig last Saturday with my Peavey Tour 700 last night. No problems during the gig, usual loudness etc, nothing out of the ordinary.

Come today and I've discovered that it has started buzzing quite loudly. It doesn't make a difference if the Bass is plugged in or not and is not affected adjust the pre or post gain.


I've been doing some research and some early models came with a triac!? But It was only the really early ones which I believe mine is not because it has the Kosmos B octaver.

I have also checked the amp with other cabs/ amp combos and it is definitely the amp so if anyone has suggestions to what it could be that would be great!

Cheers

Jake

[icastle]

A triac is use to switch mains on when a low voltage signal is applied to it, so I don't think that's anything to do with the issue you're experiencing.

Have you tried connecting the 'send' and 'return' sockets together with a spare lead?
That's often an area that fails.

[Modman]

No i've never used the send/return connections on this amp.

[mikeydee]

Agree with I castle check those jack connectors that you never use. They are not just connectors they also act as switches interrupting your signal depending on whether they are in use. Because you don't use them they sometimes oxidise and this layer of invisible rust blocks your connection. In your case it sounds like your ground connection is interrupted assuming it is a buzz like an unconnected jack input.

[3below]

Hopefully it is the send - return jack sockets suggested previously

Is it a 50hz mains hum (if you do not know this hum, measure the hum frequency with a tuning meter or phone app). If it is 50hz it is could be a smoothing (filter) capacitor in the power supply circuit. These are usually easy to replace (and very cheap) if you are ok with the soldering iron. Peavey are good with support with circuit schematics - even for kit back into the 80s.

Some very good images of the internals here [url="http://www.ajaudio.co.uk/PEAVY%20TOUR%20700%20%20AMPLIFIER%20REPAIR.htm"]http://www.ajaudio.c...ER%20REPAIR.htm[/url]

Capacitors easily accessible and the pcb tracks and pads are substantial making diy repair easier.

Edited April 22, 2015 by 3below

[mikeydee]

Moreover since the pre amp controls don't effect the level of the buzz it is safe to say that the fault is introduced after the pre amp.
Get a lead and plug it into each connector ten times and see if the fault changes. FX send return pre amp out, phones whatever you have

[Modman]

There is hum within the buzzing sound but it can be mainly heard through the tweeters of the cab more than anything.

I shall try those jack plugs that i don't use and see if this changes anything. If it does become those as the problem, how would that be remedied?

[3below]

Inserting jack plugs in and out a few times will fix that issue (if it is that issue), this will remove any oxide layer that has developed on the socket contacts. If you were keen you could put some contact cleaner (e.g. Servisol) on the jack plug before insertion.

[icastle]

[quote name='3below' timestamp='1429737681' post='2754535']
Inserting jack plugs in and out a few times will fix that issue (if it is that issue), this will remove any oxide layer that has developed on the socket contacts. If you were keen you could put some contact cleaner (e.g. Servisol) on the jack plug before insertion.
[/quote]

+1

If it is the send/return loop and the above doesn't fix it, you have a couple of options.

Either get the sockets replaced/resoldered or, as you don't use it anyway, just get a patch cable and leave it permanantly connected between the two sockets.

[Modman]

Hello everyone,

Thanks for your suggestions so far. I have tried cleaning all the jack sockets with contact cleaner and tried the patch cable for the send / return connection and none of them seem to work.

However, I have discovered that when muting the amp and increasing the post gain, the hum / buzz instantly disappears. But when unmuting with the post gain increased it comes back as it was.

Is it worth taking the amp apart and checking all the internal connections?

[mikeydee]

Yes but be careful if it is plugged in or turned on.

Sometimes the ribbon cables can be troublesome may be worth probing with a chopstick to see if you can identify the problem source.

[Modman]

Just got the lid off, checked all connections, no signs of oxidization. All ribbon cables look fine and as they should be. nothing loose or fried either, this is a proper mind boggler. May have to take a trip to amplifier A&E, bit of a shame as i was hoping for a cheap/free fix.

Edited April 23, 2015 by Modman

[3below]

My diagnosis is heading towards filter capacitor - failed electrolytic. I have 2 x Tour 700s and really like them - got rid of VBA400 as I felt they were better for what I wanted. Am hoping nothing fails on mine now as I see they have surface mount components (as will most modern, non-retro amps). I like being able to DIY my electronics repairs but am feeling this will be increasingly less so.

[mikeydee]

Yes I agree sounds like it is time to take it to an expert.

Good luck with fix.

[Modman]

Right, took it to my local guitar shop and after thorough testing they couldn't get the amp to do the same noise at all. They tested it with all my cables too and no change.

So, I bring the amp back and still the noise persists. I tried the amp with an old cab I have laying around (An Ashdown 1x12 bass cab) and the noise continues with it. I've also tried the amp and speakers in different plug sockets around the house with no change either.

I've also tried my backup amp with all the combinations but no noise at all comes from the amp. (Ashdown Mibass 220 head)

I want to say that my amp doesn't like the bergantinos but if it's doing it with the Ashdown then I am pretty stumped.

So all in all i've narrowed down my problem to the amp being at home, which is odd because i've never suffered before with problems.

Any ideas?

[mikeydee]

Perhaps the Peavey is picking up noise from the mains. Dimmer switch, refrigerator, pc. Does it do it at a friends house.?

[3below]

[quote name='mikeydee' timestamp='1430931387' post='2766108']
Perhaps the Peavey is picking up noise from the mains. Dimmer switch, refrigerator, pc. Does it do it at a friends house.?
[/quote]

Good advice, in the same vein I have one amp that is noisy at home, ok elsewhere usually.

[Modman]

No dimmer, we do have a fridge and pc in the house but none have been a problem before. It's hurting my head. I may test it at rehearsals on sunday and see if the problems occurs there.