I've got the Hot Rod Deluxe Blues and need help!

[phxbluesman]

 Ok,

  I did the frommel recap for my Hot Rod Deluxe and now I am screwed!    It was working for a bit but then nada!  No sound on either channel or when plugging directly into power amp.  I have checked the solder joints for continuity and they all seem fine.  I was bit rougher than I should have been removing some of the caps and had to repair a couple solder pads by scraping off PCB coating to reveal copper and reattatched leads.  Continuity checked ok from the lead on the component side to the solder joint of the next component on the solder side.

Here are the caps I replaced
1, 8, 9, 12, 14, 16, 19, 20, 21, 31, 33, 35, 36, 38, 39, 40, 41, 42, 43, 45, 49, 50, 56.

Here are the readings from the various test points.

Test Point            HR Deluxe Spec     Actual     
1                        4.0mV                 0     
2                        180mV                9.36     
3                        1.93VDC              0     
4                        13.mV                 0     
5                        345mV                9.3     
6                        1.93VDC              0     
7                        58mV                 -0.71     
8                        1.49V                  7     
9                        1.93VDC              221Mv     
10                      1.0V                    0     
11                      23.6V                  7.4     
12                      1.93VDC               0     
13                      1.45V                0     
14                      78mV                  0     
15                      78mV                  1.7Mv     
16                      78mV                   0     
17                      1.54V                   0     
18                      1.37V                   0     
19                      1.32V                   18.6     
20                      13.8V                  19.6     
21                      12mV                     0     
22                      1.22V                     0     
23                      920mV                 0     
24                      11.5V                 5.8     
25                      11.5V                 5.8     
26                      42.8VDC             11.5mV     
27                      66.5V                 445v     
28                      66.5V                 445v     
29                      5.34V                 0     
30                      60mV                 37.5mV     
31                      ?                       -13.47     
32               ?                        9.78     
33                      ?                       -13.52     
34                      ?                       -.497     
35                      ?                       -.577     
36                      ?                       -15.66     
37                      431V                    445v     
38                      430V                   445v     
39                      392V                    64v     
40                      345V                     64v     
41                    -106V                    0     
42                    +48VDC                 +48v     
43              -48VDC                  -48v     
44                      39VAC                  39VAC

Here are the valve voltages.. Values on pin 1 were falling.
PIN        V1          V2         V3          V4         V5
1           2.4V       2.4V       2.4V      
2           0           -0.7V      2.3mV      
3           0           10.5mV   3.7mV     445V      445V
4                                                 447V      447V
5                                                -0.52V    -0.52V
6          2.1V        2.1V        2.1V      
7           0             0          -0.81V      
8           0             0           3.7mV   37.9mV    38.mV
9               


Here is the schematic
http://support.fender.com/schematics/guitar_amplifiers/HotRod_DeluxeIII_schematic_Rev-B.pdf

I know enough to see that something is seroiusly F'd Up!    The last 3 test points are the only ones in spec.  The 37mV reading n TP30 is about half of what is should be.  And whats up with that crazy high reading on TP27 and TP28?  I triple checked that the power transformer is plugged into the correct spots on PCB board.  Red P11 & P12, Green to P13 & P14 and Brown P15 & P16  


Any suggestions would be greatly appreciated.

Thanks
JC

[phsyconoodler]

Hmmm....you were a bit rough on it,eh? I would take a close look at the ribbon cables near V1.It is easy to break those wires on some HRD's.Others seem more flxible for some reason,but some break almost instantly when you move that PC board and swing it down.

  You replaced way more caps than necessary too.
Careful is the word when working on these amps!

[tubeswell]

If the amp was working fine before the mod, and it ain't working now, then the problem is something you did to it. You need to retrace all your steps (and check the jumpers as phsyconoodler said). PCB based amps are a real PITA to work on.

[six el six]

I've found quality solder wick to be essential in taking parts off of those mexican Fender pcb.

The pcb also often need to have the solder reflowed on them.

[phsyconoodler]

Get some non-acid flux paste and rub it on the solder wick.It greatly helps with de-soldering PC boards.

[dpm309]

Looks to me like the problem might be in the power supply.  Voltages are good up until TP39 where there is only 64V instead of 390.  I would look at R74 and C35.  Maybe C35 was installed upside down?

Dan

[phxbluesman]

Looks to me like the problem might be in the power supply.  Voltages are good up until TP39 where there is only 64V instead of 390.  I would look at R74 and C35.  Maybe C35 was installed upside down?

Dan

Dan ,
Thanks A LOT for the reply!  I had to to put the test probes down for a few days.  I was seeing circuit boards in my sleep and my lady was gonna kill me if I spent any more time in the garage!  LOL.  We also had two gigs last Saturday (used my Deville) so that really wiped me out.

Okay I took your advice and made light bulb tester with a 60 watt bulb, pretty cool and reassuring I won’t completely fry my amp.  Indeed R74 was toast. Replaced it and also gently removed and tested all the caps I replaced and cleaned PCB with alcohol.   I repaired any damaged pads and reinstalled caps checking for continuity after each one.  Looks like that unclogged something because now I get a clean signal when plugging directly into power amp in (hope that means output transformer is good).  But alas no drive or clean channel.  I have an idea how the schematic flows but figured since you were right on the money with R74 you might see something obvious that could save me hours of poking around with test probes and staring at the schematic.

Thanks again

JC

Here are the latest test readings.
Seems like the power supply is working
TP HR Deluxe Spec 26-Sep
1 4.0mV 0
2 180mV 249V
3 1.93VDC 1.7V
4 13.mV 0
5 345mV 358V
6 1.93VDC 11.9mV
7 58mV 0
8 1.49V 241V
9 1.93VDC 1.85V
10 1.0V 1mV
11 23.6V 236V
12 1.93VDC 1.9V
13 1.45V 0
14 78mV .2mV
15 78mV .2mV
16 78mV .2mV
17 1.54V 0
18 1.37V 9mV
19 1.32V 186mV
20 13.8V 19.5mV
21 12mV 18.3Mv
22 1.22V 1.8Mv
23 920mV 0
24 11.5V 267v
25 11.5V 251v
26 42.8VDC 36.2V
27 66.5V 435V
28 66.5V 0
29 5.34V 0
30 60mV 60.5mV
31 ?   
32 ?   
33 ?   
34 ?   
35 ?   
36 ?   
37 431V 435V
38 430V 433V
39 392V 400V
40 345V 364V
41 "-106V" "-105.6V
42 "+48VDC" "-48V
43 "-48VDC" 48V
44 39VAC 39VAC

[dpm309]

I have a question regarding the test point voltages shown on the schematic for the HRD.  For example, TP2 and 5 are the connected to the plates of V1 and show 180mv and 345mv.  Shouldn't these be at least  200+vdc?  Same with the power tube plates and grids (450+/-VDC).  This may be a stupid question but how does Fender measure these test voltages?  Do they do it under normal load or do they introduce some sort of test signal or voltage into the signal path.

Looking at phxbluesman's latest readings, it appears that even though some of the plate and screen voltages on the power tubes do not match the schematic, they look OK when comparing them to the voltages of some of Fender's other dual 6l6 amps such as the Bassman or Bandmaster.

It looks like preamp tubetube plate readings are still way too low.  May want to recheck the power supply voltages before and after the plate resistors also.

Dan

[phxbluesman]

Dan,
Thanks again for the expert advice!
 
OK,
 
While swapping out preamp tubes to eliminate bad tubes I was getting intermittent good and bad readings on pins 1 / 6 and 3 / 8 on V1 and V2.   After tweaking how the tubes sit in the sockets as well as the tube pins the amp is working and firing on all valves now.  I had looked at the possibility of cold solder joints on the tube sockets and checked for continuity several times as well as carefully examining the joints while gently moving the sockets.  It seems to me the issue is not the solder joints but rather the pins inside the sockets especially when comparing how firmly the sockets hold the tubes in my Deville.  There is no play and they are much harder to remove/ insert whereas in the Deluxe there is a fair amount of play and they are much easier to remove and insert.   No ruling out cold solder joints ....Could cold solder joints still look OK, test OK for continuity but still fail.  The way the valves were reacting depending on which tube was in had me thinking tube failure but after a process of elimination it appears it was how the tube pins were slightly bent that was making the difference.  
 
I am going experiment some more with various tubes and see if I can bend the socket pins so they make more firm contact with the tube pins and see if that yields consistent readings.
 
The next step would be to re solder all the socket joints or replace the sockets entirely I guess.
 
Thanks again
JC
 

[phsyconoodler]

Tools to work on Hot Rod Deluxes:
-BIG magnifying lamp.
-LOTs of light.
-a good bench or work area
-patience
Wiggle tubes in sockets and look at the pc board while wiggling.You should be able to spot cracked solder joints.
-common sense.These amps are really not that complicated.They just need to be separated into sections and make sure each section is good before moving on.

Retention the tube socket pins with a needle point scribe.Get a pin straightening tool to get those tube pins straight.

[phxbluesman]

Ok...re tensioning the socket pins worked!   Amp works and sounds great!  Preamp tubes now held firmly with no play.  Woo Hoo!   Plate voltage look good. I also swapped out the 100 Kb linear taper pot for the master volume on the drive channel for a 250 kA audio taper.  Now I can ease the volume up on the drive channel instead of it blaring as soon as I get it it past “2”  At first it had me feeling like the drive channel was quieter but apparently they added attenuation (R45) to the lead circuit to compensate for the fact the put a linear taper in the first place.  A lot of guys just add a jumper on R45 and I might do that but at this point I just might leave well enough alone...LOL
 
Thanks for all the suggestion and help!