Deluxe Reverb Build

[ampgeek]

VERY nice looking build!
If you don't mind me asking...where did you get the Ruby gold filter caps? I don't think that I have ever seen those around. Sure do like the compact size!

And....I thought that MY collection of hemostats was excessive!!!

Cheers,
Dave O.

[NickC]

VERY nice looking build!
If you don't mind me asking...where did you get the Ruby gold filter caps? I don't think that I have ever seen those around. Sure do like the compact size!

And....I thought that MY collection of hemostats was excessive!!!

Cheers,
Dave O.

Greetings Dave,

Here is my source for the Ruby Gold electrolytics:

http://www.parts-express.com/wizards/se ... &srchAttr=

re: hemostats

Nothing quite exceeds like excess!

They make great heat-sinks.

If an extra set of hands is helpful in a tight spot, then 20 extra hands must be even better.

[ampgeek]

Right on Nick! Thanks for the quick response.
Never even thought of looking for HV caps at Parts Express. DUH!

Gotta love the 'stats for all sorts projects. But...you give me some serious hemostat envy!!

I also like the dental tool picky-thingys. Lots of different shapes, sizes, angles..etc...etc.. Just as handy as the hemos in the DIY amp realm.

Anyway...best of luck with the amp. Looking forward to hearing how it turns out. I really like building/playing the BF circuits (both with and without reverb). Great classic guitar tones!

Cheers,
Dave O.

[Structo]

I've seen guys move the speaker cutout in the baffle to one side or the other to clear large OT's.

Or maybe you could simply rotate the speaker, to clear?

[NickC]

Update:

I swapped the OPT; put in the Heyboer. The chassis clears the speaker easily now.

I was shy one 12AT7, so went to the local guitar-emporium and purchased an over-priced GT (Electro-Harmonix). Popped it into the PI slot and .... the heaters don't work, the tube does not pass signal. Swapped it with another 12AT7 (reverb driver slot) and it lit up and passed signal. I used a 12AX7 in the reverb driver slot in the interim testing (instead of a 12AT7) which resulted in distorted signal when pushed. I'll have to return the malfunctioning GT after work this evening, and restore the proper tube compliment.

I had some low level hum; most likely a ground loop. And I made a mistake in wiring the PCB-type cliff jacks I had for the inputs (I try not to waste parts, but those PCB-type jacks are a PITA for non-PCB applications). I stripped them out and replaced with Switchcraft switching jacks with 3/8" bushings. Used shoulder washers to isolate from the chassis. All pots and jacks are on an isolated bus with a wire running from the end of the chain to the transformer chassis ground bolt.

I had the reverb/vib panel jacks isolated as well, with a lead grounded to the reverb transformer bolt. I tried bolting the jacks to chassis without the isolating washers, and with the ground at the reverb transformer bolt, which did not help eliminate the hum. I'll revisit that, replace the isolation/shoulder washers and run the ground lead back to the PT mounting bolt (star) ground.

I also consider one (or more) tubes may be faulty. I purchased a bunch of Sovteks when a local music store was going out of business 15 years ago. Turns out some were in the wrong boxes ..... which is how I found myself shy of a 12AT7. No access to a tube-tester, so it'll be trial and error.

I added one more mod; removed the second speaker jack and installed an inline switch. In the default "on" state it passes NFB signal to the speaker jack connection. "Off" setting removes NFB.

More info to follow as this project develops.

[Firestorm]

Progress! You might want to try splitting your grounds. The main filter and tube cathodes have a lot of stuff on them, so by connecting that back to the preamps along a single buss, you're putting some unwanted "signal" on your inputs. Maybe ground the main filter, screen filter, PT center tap and output tube cathodes where you have them now, but lift the preamp ground buss from that and make a new ground near the input jacks. I'd think the rev/trem jack grounds would have been good at the rev tranny bolt. The reverb footswitch is connected to the rev recovery tube grid, so it needs a quiet ground. I don't know what kind of reverb tank you're using, but the originals only need the output side grounded.

[NickC]

Progress! You might want to try splitting your grounds. The main filter and tube cathodes have a lot of stuff on them, so by connecting that back to the preamps along a single buss, you're putting some unwanted "signal" on your inputs. Maybe ground the main filter, screen filter, PT center tap and output tube cathodes where you have them now, but lift the preamp ground buss from that and make a new ground near the input jacks. I'd think the rev/trem jack grounds would have been good at the rev tranny bolt. The reverb footswitch is connected to the rev recovery tube grid, so it needs a quiet ground. I don't know what kind of reverb tank you're using, but the originals only need the output side grounded.

Thank you!

I have separated the grounds for the power supply filter cap board. The caps associated with the preamp are grounded to the buss wire soldered to the backs of the pots and connected to the jacks. I bolted that ground to the chassis next to the normal-channel-input jacks as you recommended. The other ground leads go to the PT mounting bolt ground point.

Set bias (using Weber Bias meter). The 6V6s are fairly closely matched.

I checked voltages at all tubes, which were all in proper range (423 VDC on octal plates, range from 193 VDC to 167 on the dual-triodes .... close to expected values). However, one 6V6 began to red-plate within 30 seconds of taking off stand-by while playing guitar through the reverb channel. Flipped the stand-by immediately and swapped the output tubes. The problem followed the socket, not the tube. It appears the onset of red-plating occurs under load, and not at idle with the standby off. Or perhaps it would merely take longer for the red-plating to manifest at idle?

Metered the 470R and 1k5R on each 6V6 socket and got correct measure. I traced the circuit to the board, checking continuity of every wire. Even though I had drained the power supply caps (and verified with DMM) I got a nasty shock when I nudged a .1uF Mallory cap (connected to PI pin 1) a few mm over so it wasn't as close to the NFB resistor. Didn't expect that. Hand tingled through half the next day.

The normal channel isn't passing signal. Triple checked the wiring, which looks correct. Next I'll check each component.

Re-flowed solder on all tube sockets, and every connection in the affected circuits.

I'll get of the signal tracer tonight and start methodically working through the circuits for the normal channel and output section to find the faults. Could be a bad cap, or a bad ceramic octal tube socket.

Getting close, I think.

[Firestorm]

Set bias (using Weber Bias meter). The 6V6s are fairly closely matched.

What did you set the bias to?

Even though I had drained the power supply caps (and verified with DMM) I got a nasty shock when I nudged a .1uF Mallory cap (connected to PI pin 1) a few mm over so it wasn't as close to the NFB resistor. Didn't expect that. Hand tingled through half the next day.

When you drain the caps, the standby switch has to be closed or you'll miss the preamp PS. Was it? Caps can rebuild their voltage after being drained, so it's best to leave a grounded jumper on one while working.

The normal channel isn't passing signal. Triple checked the wiring, which looks correct. Next I'll check each component.

I can't see how the output of V1b is connected to its 220K mixing resistor. Under the board? Check that connection.

[NickC]

What did you set the bias to?

19.6 mA

When you drain the caps, the standby switch has to be closed or you'll miss the preamp PS. Was it? Caps can rebuild their voltage after being drained, so it's best to leave a grounded jumper on one while working.

I had the amp in stand-by mode (standby switch engaged).

After draining caps (with 3-prong power cord plugged in) I always unplug from wall power. But I haven't used grounded jumper .......... which now becomes standard safety protocol from this day forth. Thank you for the excellent advice.

I can't see how the output of V1b is connected to its 220K mixing resistor. Under the board? Check that connection.

<slapping my forehead and saying to myself in my best Homer Simpson voice "DOH!">

How'd I miss that? The V1b (pin 6 to .047uF) to the 220k R ---> .001uF ----> Phase Inverter pin 2. That must be one of my very best senior moment goofs yet! Embarrassing.

Thank you again.

[Firestorm]

Standby has to be in the "play" position to drain all the caps. The jumper is still a good idea.

As to the bias problem, since it follows the socket, check the coupling cap on that side. If it leaks, there goes your negative voltage. Also look for any stray connections along that grid lead: wire "whiskers," solder blobs, etc. that may provide a place for the bias voltage to "escape."

[NickC]

Standby has to be in the "play" position to drain all the caps. The jumper is still a good idea.

As to the bias problem, since it follows the socket, check the coupling cap on that side. If it leaks, there goes your negative voltage. Also look for any stray connections along that grid lead: wire "whiskers," solder blobs, etc. that may provide a place for the bias voltage to "escape."

Success!

The culprit was the 82k R that goes to Phase Inverter pin 1. Replaced it and the amp works. The tone is sweet, and the hum is gone. Output tubes are behaving themselves (no red-plating after 15 minutes playing through it).

I have a few adjustments before fitting in the cab. I'm draining the caps with the standby switch in the "play" position right now(power off, cord plugged in for a ground path).

I have the power and fuse wired up old-style Fender (with the fuse inline on the cold side, switch inline on hot side). I'm changing it to have the power switch and fuse in series on the hot AC leg and solder (telegraph lineman style) the cold incoming AC line cord directly to the other transformer primary lead and secure with a couple layers of heat-shrink tubing.

Looking at the Mercury Magnetics wiring diagram for the PT, it shows primary wiring as:

0V Black

120V White

This implies the white primary wire should be connected to the black (hot) wire coming from the AC line and the white (cold/neutral) AC supply wire to the black primary PT lead .... which is opposite to standard convention for common house wiring?

Seems odd to me. But maybe Ralph Waldo Emerson was correct when he said "A foolish consistency is the hobgoblin of little minds." Maybe I'm foolish and/or small-minded, but it seems some consistency with standard electrical code would eliminate confusion.

I am grateful for the advice and counsel! I'll post some pictures upon completion.

[C Moore]

So what was wrong with that 82k exactly.?

[NickC]

So what was wrong with that 82k exactly.?

Maybe a manufactures defect, or rough handling in packaging/handling .... or I may have stressed the lead, where it enters the body, when installing on the turret. I always use two needle nose pliers to bend leads; one to support the body of the component and the other to do the bend. Even so, I may have stressed it wedging it into the turret.

It looked like a solid connection visibly, but the DMM said otherwise. It tested much lower than 82k, but the meter reading was intermittent (which I attributed to the cap next door). Decided to lift the end by the cap and then test it as well as the cap. Applied the iron, gently lifted, and the lead separated right where it enters the body ..... with the rest of the lead still in the turret. Cleaned up the turret. Popped in a known/tested good 68k R, and all is well.

.

[NickC]

Finished pictures:

Gut
[img2304]http://homepage.mac.com/swamptone/DRGut.jpg[/img]

Gut2
[img2304]http://homepage.mac.com/swamptone/DRGutLeft.jpg[/img]

Front
[img1728]http://homepage.mac.com/swamptone/DR1.jpg[/img]

Back
[img1728]http://homepage.mac.com/swamptone/DRBack.jpg[/img]

Logo
[img1728]http://homepage.mac.com/swamptone/DRLogo.jpg[/img]


Non-standard Features:
(1) rear-panel switch to remove NFB
(2) switch on Vibrato intensity pot to remove "Vibrato" from circuit
(3) extra fuse-holder

It sounds good, like a Deluxe Reverb should. Removing the NFB makes for a more aggressive sound. I am very pleased.

Thanks to all for the kind assistance with this project. I am most grateful.

Best Wishes

[rdjones]

Logo
[img1728]http://homepage.mac.com/swamptone/DRLogo.jpg[/img]

Cool logo !

rd