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FDP Forum / Amp Mods, Repairs, and Projects / BDRI is has a hum going on

Therealfrogman
Contributing Member
******

Pueblo, Co

illegal is a sick bird....
Dec 2nd, 2017 11:38 AM   Edit   Profile   Print Topic   Search Topic

Just started a couple days ago, it is not super loud but it is annoying. Sounds like an open ground would on a guitar (my best description of it) I had the caps replaced by a pro a couple months ago so I am pretty sure it is not the caps.

It hums with nothing plugged in and it does not get louder turning up the volume. I did a search for humming and found little.

Cal-Woody

USA/California

Why do I keep fixing things that work?
Dec 2nd, 2017 12:32 PM   Edit   Profile   Print Topic   Search Topic

I almost think that it's a bad input jack. These things fail regularly and probably needs replacement. The internal guts of these short out and hum like crazy!
Maybe Willie or another tech will jump in here and confirm my thoughts, as you have had most of the other components replaced already and the input jack seems most likely to me.

Cal-Woody

USA/California

Why do I keep fixing things that work?
Dec 2nd, 2017 12:37 PM   Edit   Profile   Print Topic   Search Topic

I almost forgot to mention to check the effects loop jacks, because they can get dirty and cause weird things also.
So, spray some electronic cleaner on a 1/4" jack and run it in and out of all your input jacks and maybe something there is causing a problem. It's just good practice to check all of your input jacks and be sure that they are not a contributing factor.

Therealfrogman
Contributing Member
******

Pueblo, Co

illegal is a sick bird....
Dec 2nd, 2017 12:59 PM   Edit   Profile   Print Topic   Search Topic

Thank you for the quick response. I have de-ox I will try what you suggest.

Therealfrogman
Contributing Member
******

Pueblo, Co

illegal is a sick bird....
Dec 2nd, 2017 02:49 PM   Edit   Profile   Print Topic   Search Topic

Nothing good happened with that. I wish I knew more about this stuff but then again when it came time to replace the leaky caps I chickened out.

pdf64

UK

Dec 3rd, 2017 02:18 AM   Edit   Profile   Print Topic   Search Topic

Note that the acronym 'BDRI' can be used for 2 models, so whilst better than nothing, it isn't super helpful.
I've linked to the Blues Deluxe RI schematic, hoping for a lucky shot.

Re-seat all tubes a few times; any improvement?

Does the reverb control, or plugging into the power amp input, or removing the tube in V3, affect the hum?

If none of the above mutes it, try a known good pair of MATCHED power tubes, with the bias control adjusted appropriately, as per schematic.

Blues Deluxe RI schematic

Roly
Contributing Member
**********
**********
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Whitehorse Canada

I don't get out much
Dec 3rd, 2017 02:23 AM   Edit   Profile   Print Topic   Search Topic

If the hum is not affected by the volume control, that means (to me at least) that the problem is upstream of the volume control.
I agree with Cal, the jacks are crap, (if it's one of the Deville type amps). but if the volume has no effect on the hum, I would look elsewhere.
BDRI is Greek to me.
I get the reissue part but not the BD part.
Enlighten me.
If the amp has an effects loop, try sticking a guitar cord in the effect send, don't connect it to anything..hum still there?
If so stick it in the effect return connected to your guitar...still there?
If so...pull all the 9 pin tubes,except the phase inverter tube, note which hole each tube was removed from.
Gone? If not pull the phase inverter tube.
Gone? If not, something is aims in the power section.
Perhaps power tubes, perhaps caps. New caps can fail.

If you try what I suggest and reply with details, the resident big dogs will have more information to base their replies on.

cheers


Roly
Contributing Member
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Whitehorse Canada

I don't get out much
Dec 3rd, 2017 02:49 AM   Edit   Profile   Print Topic   Search Topic

I forgot to add....If the hum is gone when all nine pin tubes, except the phase inverter, are removed....add the removed tubes one at a time from left to right when viewing the amp from the rear, and note when the hum returns.
Sorry for the omission.

cheers

Therealfrogman
Contributing Member
******

Pueblo, Co

illegal is a sick bird....
Dec 3rd, 2017 01:36 PM   Edit   Profile   Print Topic   Search Topic

Blues Deluxe Reissue, sorry. I just gently reset each tube, I did not pull them out all the way. The hum is gone. I need all of these tubes in for this thing to work right? I see 2 6l6 tubes and 3 smaller power tubes.

Roly I am confused.

Cal-Woody

USA/California

Why do I keep fixing things that work?
Dec 3rd, 2017 03:05 PM   Edit   Profile   Print Topic   Search Topic

The first 2 tubes are used for the preamp section and the third, closest to the power tubes is the phase inverter tube. If you pull both of the preamp tubes there will be No Sound sent to the power section of your amp. The phase inverter tube should always be inplace or the voltage to the bias supply will not work and send the wrong voltage to the power tubes and maybe fry your amp! When checking the phase inverter tube, the power tubes should be removed in a live circuit.
Turn off the amp and spray each of the tube pins with contact cleaner and re-insert the tubes into their sockets and this will help to clean up the pins and will improve your connection, thus making for a better contact and improved performance.

(This message was last edited by Cal-Woody at 05:07 PM, Dec 3rd, 2017)

Bubbalou

USA

THE LOW END OF UPPER TEJAS
Dec 3rd, 2017 08:57 PM   Edit   Profile   Print Topic   Search Topic

Also with tube removed inspect the socket under good lighting conditions and see if any of the "pin tubes" on the socket looks larger diameter than the others.

Roly
Contributing Member
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Whitehorse Canada

I don't get out much
Dec 3rd, 2017 11:02 PM   Edit   Profile   Print Topic   Search Topic


My apologies for my somewhat cryptic remarks.

Cal....why do you think pulling the phase inverter tube will affect the bias voltage?
Just for reference,I have a Super Reverb on the bench.
Bias voltage does not change when the phase inveter tube is removed.

cheers

pdf64

UK

Dec 4th, 2017 05:20 AM   Edit   Profile   Print Topic   Search Topic

I think that if pulling the phase splitter affected the bias voltage, then it would indicate that the coupling caps between the phase splitter and power tube control grids are leaking dc.
Which is a bad thing.
It may happen as pulling the tube would stop there being any voltage dropped across its plate load resistors, so the voltage across the coupling caps would increase around 100Vdc.

In normal circumstances, pulling the phase splitter tube would have no affect on the (necessarily idle) operating conditions of the power tubes. I would have no hesitation about doing it.

(This message was last edited by pdf64 at 07:22 AM, Dec 4th, 2017)

Cal-Woody

USA/California

Why do I keep fixing things that work?
Dec 4th, 2017 06:35 AM   Edit   Profile   Print Topic   Search Topic

I actually didn't know for sure, so I thought maybe it could damage the power tubes and sought caution.

STR87

Panama

Dec 4th, 2017 11:44 AM   Edit   Profile   Print Topic   Search Topic

Happened once to me, bad preamp tube.
Get some know working preamp tubes and replace the old ones. Use a little Deoxit and work the tubes in and out a few times, if they feel loose try retensioning the tube sockets.

FDP Forum / Amp Mods, Repairs, and Projects / BDRI is has a hum going on




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