Blues Deville Lack of output volume

[shortfuse]

I have a blues deville Type PR247 212 combo that has very low volume output.  Both channels work but the volume output is very low.  I think it should be biased at about 46 it is reading 41 so I don't think that would be it?  I have not tried different power tubes as I do not have any other 6L6's around the house.
I Checked voltages http://www.el34world.com/charts/valve/ValveData.php?e=view&f=16434
Schematic attached - I think this is the correct one I got it from the library
The plate voltages V1 - V3 seem very high to me.  I think I also need to check V2 - 6 again as I got 0 voltage reading
Caps read as follows:  41 & 34 are the main caps and read voltage on both sides but looking at the schematic they feed 42 and 35 would this be correct or could this be part of the problem. 
C41 +489/240
C42 +241/0
C34 +490/234
C35 +233/0
C45 +438/0
C46 +393/0

[stratele52]

V2- 6 ; 0 volt !!!  Sure this half tube are not used in the amp, 6-7-8 = 0 volts

Look here , same problem/ same amp as your few days ago .You can read the trouble shooting. Found something .

http://forums.fender.com/viewtopic.php?f=12&t=91049

[shortfuse]

Thank you read through the thread same amp same year sounds spot on to my problems.  Going to try a few things you suggested in that thread on my amp tonight.  Will report back later.

[stratele52]

Thank you read through the thread same amp same year sounds spot on to my problems.  Going to try a few things you suggested in that thread on my amp tonight.  Will report back later.

+1

[LooseChange]

First, there should be voltage on V3 Pins 2 and 7.
Check to see if the power amp works by plugging something into the Power Amp In jack.
Report back.

[stratele52]

First, there should be voltage on V3 Pins 2 and 7.
Check to see if the power amp works by plugging something into the Power Amp In jack.
Report back.

Pins 3-8 have 33 VDC so pin 2 and 7 must have less.

IMO all tubes may show good voltages , even if signal path is open or short = low volume

[shortfuse]

LC thanks for your input.  I plugged an iPod MP3 player in o the power amp and same thing very low volume even with the volume on 10.  And the best word to describe the sound would be fuzzy.

Stratele52 in the other forum you suggested to by pass the power amp jack and circuit.
"Disconnect the wire from R20 at J3 pin 4 ( Power amp jack ) and disconnect from C 14 at J3-8 . Connect R20 to C14 . Amp should sound louder if there is problem on J 3 or short there.
Check ohms to ground , must be very high ohms reading .
To test J3 ? ; Disconnet all wire at J3 an read contact as show on schematic"

I have not attempted to remove the main board yet as that would be the only way to accomplish that.  But may be my next move.

[stratele52]

shortfuse ,

If J3 contacts are wrong / dirty you may loose some power . There are so many things to check about your low volume . Try to bypass J3 contacts with some jumper or wire if you want to be sure.

You must know where you loose the power . On the other tread we loose the power before J3. 

Same for your amp ? Chance you have wrong resistors in Phase Inverter circuit. 12XX7 before outputs tubes.

[LooseChange]

Do you get reverb? what happens when you give the amp a bit of a shove... Anything intermittent?
With an audio source plugged into the power amp in jack you have narrowed the problem down to the reverb recovery/mix (U2), the PI and the power tubes.
In all the HRD's I've repaired I've only replaced one Op Amp. This problem is usually due to the plate resistors on the PI tube. Check those again. If not that, check the power supply to the Op amps.

[shortfuse]

LC Reverb works fine just low in volume with the rest of the amp.  Jarring the amp tapping components and tubes with a chop stick revel nothing.  All plug in connectors i have unplugged and replugged back in to insure they have good connection.  Transformer, ground connections reverb connections ect...  I will check plate resistors to the PI tonight.
I quizzed my friend that owns the amp again last night about exactly what happened when this all happened.  Said he plugged his digitech preamp into the power amp input and was playing and that is when it happened.  This was several years ago and has been sitting in his garage until i offered to attempt to fix it.  Doesn't the switch on the power amp input cut out the main on board preamp to the amp meaning all the preamp tube section?  Is it possible that something in that circuit popped?  And Stratele52 if i do as you suggest jump from r20 to Q14 that bypasses the power amp in circuit and let me get back to the main preamp to see if it is working as it should?  Can this be jumped without lifting a leg?
I do not have a signal generator or a listening device for guitar amp repair per say.  But could I use an mp3 player to the input jack and or power amp in jack then use a listening device I have for phone repair (it is a probe with a speaker in it) that checks for dial tone and then follow the circuit to the point where I loose volume/signal?  Or I have seen a few schematics for making a listening device maybe radio shack has one?  I guess my question is would a listening device and signal generator be the next step before lifting components from the board?  Forgive my ignorance I am in uncharted waters here I'm a 5 tube non ic/circuit board kinda guy.
I appreciate the help and suggestions.

[stratele52]

  Transformer, ground connections reverb connections ect...  I will check plate resistors to the PI tonight.


I appreciate the help and suggestions.

Who is talking about PI plate resistors ?

I write ALL resistor on PI circuit.

Fot you other questions , sorry I should live home for the day.

[jjasilli]

1.  I have not tried different power tubes as I do not have any other 6L6's around the house.  Always suspect tubes first. 

2.  I Checked voltages http://www.el34world.com/charts/valve/ValveData.php?e=view&f=16434   The schematic has numerous Test Points each with a specified voltage.  These need to be checked too.

[stratele52]

1.  I have not tried different power tubes as I do not have any other 6L6's around the house.  Always suspect tubes first. 

+1

2.  I Checked voltages http://www.el34world.com/charts/valve/ValveData.php?e=view&f=16434   The schematic has numerous Test Points each with a specified voltage.  These need to be checked too.

With low volume , most of the time voltages are good , but it is always second thing too check , first are tubes.

 

[shortfuse]

Had the power tubes checked out Tuesday afternoon before I did anything else and they all checked out ok on his tube tester.
Going to look closer at the PI circuit as LC suggested before I get into removing the board and lifting components.  Also going to verify voltages at the test points as suggested and as shown on the schematic.  Will get deeper into this tomorrow evening.
Thank you for the comments and suggestions.

[stratele52]

Had the power tubes checked out Tuesday afternoon before I did anything else and they all checked out ok on his tube tester.

Most , if not all, tubes tester can't  test amp's tubes . If your tubes have the right bias on your amp, they are not causing the problem of low volume.

[shortfuse]

Here is what I have done. 
I have tested all grid and plate resistors and all appear to be within tolerance according to the schematic.
I then disconnected and jumped R20 & C14 to by pass the power amp in switch no change in volume or performance at all.
I then built a signal listening probe, downloaded a free signal generator for the i phone, and thank you sluckey for simplifying the listening device I used another amp.  Although I will probably make one like Eleventeen suggested out of an amplified computer speaker as it is portable and much smaller.  That was in this thread http://www.el34world.com/Forum/index.php?topic=15893.0
I listened from grid to plate hoping to find something not working or sounding different.  I had signal and amplified signal from V1 - V4 & 5.  Good signal to V4 & 5 pin 5 but fuzzy and lower signal pin 3.  What does this mean?  Are the tubes bad even though they test good and voltages seem ok, as it is before the OT.  Or do i possibly have a bad transformer?

As for the voltage test points, most say value in VAC (volts AC?)  How are these test points used?  with a signal generator?  I could not get any of these points to test correctly, I am sure I am doing something wrong and someone will set me straight.

[Willabe]

As for the voltage test points, most say value in VAC (volts AC?)  

Yes, VAC = ac volts.

How are these test points used?  with a signal generator?  I could not get any of these points to test correctly,

The schematic has numerous Test Points each with a specified voltage.  These need to be checked too.

This is what JJ was talking about.

Most of the time it's enough to just check the dcv's to find a problem, find/correct a missing or way low dcv and it's fixed.

Now if they look good we know the B+ power supply is (should be) fine and we know that the tubes are getting plate dcv and if we have a dcv at the K then we know the tube is drawing current.

But if all that is fine then a next step can be checking for acv's at each stage.  

To get the tube stages to put out an acv it has to have an acv coming in to amplify. No acv in no acv out. Look at J1, it says 4mvac at the input. Look under the OT in the schemo, says, Output test 1khtz into 8 ohm.

So I think their saying to get the VAC voltages at the test points they show, they injected a 1khtz @ 4mvac into the input jack.

http://www.el34world.com/charts/Schematics/files/fender/blues_deville.pdf


          Brad    

[stratele52]

Here is what I have done. 
 
  What does this mean?  Are the tubes bad even though they test good 

 

They test good on tube tester or with new one ?

Most tube tester can't test guitar amp tube

[stratele52]

Most of the time it's enough to just check the dcv's to find a problem,

           Brad    

Not in my opinion

[The_Gaz]

Are you sure you are not accidentally plugged into the extension jack? It gives the exact symptom to are describing.

[shortfuse]

Gaz
Thank you for the suggestion I am plugged into the jack that has the green yellow which according to the schematic is the main jack the one with the wiring coming from the OT shows ext speaker which seems backwards to me but the way the jacks short out is why it is I guess.  I did not have time this weekend to double check the jacks to make sure they are making good contact and shorting correctly as someone else suggested so I will do that tonight.

[shortfuse]

Speaker jack is the culprit.  On top of that I do believe I may have plugged the speakers into the wrong jack when I pulled the chassis and was tracing the signal path last Friday.  LC suggested the speaker jacks and contacts to me last Tuesday after I plugged into the power amp in jack and reverb worked and got sound.  So it was a combination of a bad part and a still learning hobbyist.  Once again it was a simple problem that I tried to over overthink or over complicate.
Thanks to all for your comments and suggestions.  I did learn a few things during this one.  Learned to double check the obvious, easy to get to and most used pieces 1st then dig inside.  Learned to make a signal tester and how to use one.

Now that I have volume the drive does not seem to be working as it should as it is very clean sounding.  I have played through one of these before and I remember it crunching pretty good with the drive turned up.  More stuff to trace down this week I guess.

[shortfuse]

Now that I have volume the drive does not seem to be working as it should as it is very clean sounding.  I have played through one of these before and I remember it crunching pretty good with the drive turned up.  More stuff to trace down this week I guess.

According to a few people I know that had one of these amps say the gain I have is all I will get.  Played this amp tonight and I think it sounds very good just wish there was a little more crunch in the drive knob.  Is there a mod out there that utilizes V2b for more gain?

[PRR]

> wish there was a little more crunch in the drive knob

Put 22uFd (2uFd-50uFd) across R10.

This will also change the Clean gain. Run the Volume knob a bit lower to compensate.

[shortfuse]

Thank you PRR this did the trick not like a hot rod deville but a mild bluesy crunch.  Actually it sounds great cranked on the clean channel and rolling the vol off to clean up.
Thanks again