Sluckey's Trem-O-Nator (replacing the roach with VLT5C1) AB763 Super Reverb

[72Blazer]

Gent's I am building from scratch the AB763 Super Reverb (head cab).  I currently have the fender style eyelet board populated using the roach for the vibrato.  I've successfully built the the stock AB763 Super Reverb before but this I'd to use Sluckey's Trem-O-Nator mod.  The problem is I am working off a "layout" because I am not "schematic" savvy.  I am trying to crack the code.  It can't be as simple as just swapping out the roach with the VLTC51 correct?  Are there other component to swap out?  If I were using the Hoffman layout I found examples of that.  Again, I am using the stock fender eylet board layout.

Vr
J.

[sluckey]

Read this. It's for a Pro Reverb AB165 but the board is the same as the Super Reverb...

     https://el34world.com/Forum/index.php?topic=24603.msg265142#msg265142

[72Blazer]

Will do!

That thread is a keeper for sure.  Got a few tools in the fire right now now but I will report back soon.  Muchos Gracias!

Vr
J.

[72Blazer]

Studied the modified layout you pointed me to and this circuitry actually saves you money by eliminating 2 bypass caps.  Very cool.

[sluckey]

Studied the modified layout you pointed me to and this circuitry actually saves you money by eliminating 2 bypass caps.  Very cool.

Gee, you think? Now if you could just get your money back for that wasted half 12AX7.   

[72Blazer]

I'm laughing now too.

[72Blazer]

Got a question:  On this drawing where does the wire (x) that connects to junction of 47k and 1 Meg resistors go and where does the wire (x) that connects to the two .01 caps go?  Thanks.
Vr
J.

[sluckey]

That ain't my drawing! I'll only answer questions about my drawing.   

Better throw that away and use only the "pro_trem_mod.pdf" in reply#4 of the link I gave you if you want this mod to go smoothly and be successful. I'm gonna attach that same file to this message so you will be sure to use the only file that applies to your mod. This file is all you need. Don't muddy the water!

[72Blazer]

Thanks,

I sure did mix things up.  Thanks for the correct vector.

Vr
J.

[72Blazer]

Question for Sluckey:

Is the white wire in the drawing above still needed?  It originally connected to the bias board.  If its still need I am not sure where to hook the other end?

[sluckey]

Not needed.

[72Blazer]

Thanks!  That sure was a head scratching moment!

[sluckey]

Why? If the white wire was already in place, just leave it alone. It will be soldered to an eyelet that has nothing else connected. But if you have not yet installed that wire, then don't. The bias connection was used by the original fender tremolo but is not needed by the Trem-O-Nator. Look at the schematic to understand what that white wire did.

[72Blazer]

Ok so this new AB763 Super Reverb Build is in progress/trouble shooting mode.  Besides this tremonator mod, I have also attempted/wired RobRob's "Lead Channel" Mod as seen here:

https://robrobinette.com/AB763_Modifications.htm#Lead_Channel_Mod

I figured I would start here with determining if I correctly installed this VTL5C1 I purchased from Ebay:

https://www.ebay.com/itm/232435381414

My question is how do I determine correct orientation?

I followed the layout according to the "pro_trem_mod.pdf" above in this thread.

I've got it mounted on the fender style eyelet board with the stamped "sr VTL" face up and the long leads are facing the tone/volume control side of chassis.  One lead is going to ground and the other lead is going to the middle lug of the 50K tremelo intesity pot as depicted.  The shorter 2 leads are wired per the pro_trem_mod.pdf as well.

Other information:  This amp now powers up but volume is almost nothing.  All tubes are heating up.  All pre amp tubes came out of a working Fender Deluxe Reverb amp.  The rectifier and Output tubes (GZ34 and 6L6 GCs) appear to be ok as far as I can tell.

I've documented the tube voltages.  Measurements were made after ensuring -52v going to the output tubes.  These tubes are not matched.  I installed 1ohm resistors on pin 8 to ground and measured 26 and 31 mA respectively.

Tube Voltages:

Rectifier: Pin4: 380  Pin6:379

Output (V8)     Output (V7)
Pin3: 465v       Pin 3: 465v
Pin4: 464v       Pin 4: 463v

Pre Amps:
V6 (12AT7)    V5 (12AX7)   V4 (12AX7)   V3 (12AT7)   V2 (12AX7)   V1 (12AX7)
Pin 1: 245v    Pin 1:  303v  Pin 1: 280v    Pin 1: 460v    Pin 1: 275v  Pin 1: 242v
Pin 3: 100v    Pin 3: 3.15v  Pin 3: 3.98v   Pin 3: 10.2v   Pin 3: 2.2v   Pin 3: 2.0v
Pin 6: 245v    Pin 6: 445v   Pin 6: 280v    Pin 6: 460v    Pin 6: 280v   Pin 6: 291v
Pin 8: 101v    Pin 8: N/A     Pin 8: 3.9v    Pin 8:  10.4v  Pin 8: 2.18v  Pin 8: 0v

In retrospect, I think I should have built to original spec-ensured a functioning amp-then attempted mods.  I just wanted to see if I could pull this off.  I've obviously botched something here.  I've spent about a day now tracing wires and checking vlues of caps and resistors, but still have not found my mistake (s).

I'll post pics if needed...
Vr
J.

[72Blazer]

After reviewing the spec sheet for the VLT5C1, using my TC-1 mutifunction tester, I was able to discern the resistor side (leads) and the LED side (leads).  too include which lead was the positive side.  Then looking at pro mod layout above, I am certain I've got this oriented correctly on my board.

The short jumper from the junction of the 1Ms to ground was added as well as a jumper between the plus side of the VTL5C1 to that 10K resistor.

Still need to further T/S the extremely low and somewhat distorted volume.

[72Blazer]

OK,

I found my biggest mistake and that was I had the speaker output jacks wired wrong.  Good volume now and the Trem-O-Nator is functioning as well as reverb  I have a constant buzz.  I'll have to figure out if its a 60 or 120hz and more/different/higher pitched noise when the reverb level is increased.

The humm/buzz is in the vibrato/reverb channel only and intensifies/responds with the volume increased.  It really sounds like a 60hz tone.  Hum goes away when this channels volume knob is turned all the way down.

Normal channel is very quiet

[72Blazer]

This Trem-O-Nator mod is really awesome 

Thanks Sluckey!

Be gone roaches!