"New" SFPR reverb problem?

Stubee · February 3rd, 2008, 03:30 PM

You guys helped convince me a Princeton Reverb was a good amp, and you were right. Just got a SFPR with BFPR chassis. Very nice overall & the tone is wonderful. Pics later, but a question on the reverb:

This has new tubes, caps, reverb tank, but the reverb just doesn't have much "verb". I compared it with my old MusicMan RD112-50 (original reverb tank): The MusicMan reverb on "1" is probably stronger than the Princeton at "10". The SFPR 'verb does change the amp tone when used, but it's a very faint effect The vibrato works fine & strongly.

So I looked at the tubes. All amp tubes glow brightly & evenly except for the farthest right (looking at the back of the cab). That one (12AT7?) is barely lit at all; I had to look closely to see if any current is going through it. It's only lighting up the filament at the very end (glass end) of the tube & barely gets warm. I removed the tube, put it back in. It seems to seat well.

I've contacted the seller to get his advice, but DK when he'll be able to respond so am asking you guys. Bad tube or do the reverb tubes not draw much current? I did the search & see all the info on bad tank leads, but wonder about this low-glow tube.

Any ideas welcome, thanks.

skeksis · February 3rd, 2008, 03:55 PM

I'd suggest checking to make sure the new tubes match the tube chart... and trying a different tube in the reverb send/return slots. V1 (furthest right) ought to be a 12ax7 or 7025, V2 a 12at7, V3 12ax7, V4 a 12ax7.

if V2 (reverb send) is bad, or maybe V3 (reverb-recovery, which might only be half-bad), you might get the symptom you describe. make sense?

Wally · February 3rd, 2008, 03:57 PM

If the filaments are glowing, I don't think that the problem. Different tubes have different 'visibility' of the filament glow. I am not saying that that tube is good but that I think the filament is not the problem. If you have another 12At7 or even a 12ax7, sub it into that V2 position and see if there is a change. The reverb return is one-half of V3 (12AX7). If the sub into V2 doesn't help, sub into V3. If that doesn't help, the problem lies elsewhere.....tank, reverb transformer, cap, resistor, pot..lots of possibilities.
That reverb should get into surf territory. Does the reverb 'crash' when you hit the amp or rock it? If so, the return might be fine and the problem may lie in the send part of the equation.
FWIW, I consider it prudent to have a newly acquired amp evaluated by a good tech. Just because it is making sound doesn't mean everything is as it should/could be.

Stubee · February 3rd, 2008, 05:02 PM

The seller numbered the tubes & told me what order to put them in, as he'd removed them for shipment (and packed the amp like a tank). I don't think I have another pre-amp sized tube laying around but will check, I can always get one somewhere.

No, it doesn't seem to "crash" like my MusicMan does when bumped a bit but I didn't bump it much to test.

As far as filament "glow", let me clarify: I thought this tube was completely out, I could only see any sign of charge when I really stared at the bulb end for a bit, and there sure ain't much there. Play it for 45 minutes, that tube isn't hot but barely even warm. I think the only reason it's even above room temperature is because of the heat from the adjacent "glowing" tubes. I mean, this thing ain't glowing.

I'll also look up the schematics on this thing so I understand what tube is doing what (V1 etc.).

Arggh...this amp was just completely redone by the previous owner & he sounded like he knew his business. I hope it doesn't need an amp Dr. cuz there ain't one around here & it sounds great except for the 'verb. Thanks much,

Stubee · February 3rd, 2008, 05:40 PM

OK: I did a coupla things:

*Pulled a 12AX7 outta my good little Pro Jr. That tube glows brightly in the Princeton in the V1 port, but didn't add any reverb whatsoever. Didn't have time to mess with other tubes right then.
*Bumped it a couple of times. Yes, it does "crash", but it is faint and about 5%-10% the noticeable crash ya get when ya bump my MM or the older Fender Reverbs I used to have. It is very faint.

Then the seller answered me. He said this may be the amp that he changed the reverb return/mix resistor on because it had too much reverb for his use. He's checking his records so I'll wait to here on that. If that's the case, wish he'd told me. I don't use it much anyway but if it's there, I want it working.

Dacious · February 3rd, 2008, 06:30 PM

Try flipping the reverb leads over on the back of the chassis. Oldest trick in the book with a Fender, putting them on the wrong way around.

Result is no 'verb.

Stubee · February 3rd, 2008, 11:49 PM

Dacious: flipped the leads. Result: no difference, though it did seem to take away the very faint "hum" I got with the reverb cranked to 10.

Darn, I liked that solution. Well, I'm waiting back to hear from the guy on the "resistor" and will look at the rest of the tubes tomorrow. Thanks,

jh45gun · February 4th, 2008, 12:06 AM

Quote:

Originally Posted by Stubee

Then the seller answered me. He said this may be the amp that he changed the reverb return/mix resistor on because it had too much reverb for his use. He's checking his records so I'll wait to here on that. If that's the case, wish he'd told me. I don't use it much anyway but if it's there, I want it working.

That would make me wonder why anyone would do that as you don't want as much reverb that is what the pot on the amp is for turning it up or down. Hearing that would sure make me wonder though any screw ups some one did of course you can put back to the origional configuration.

Stubee · February 4th, 2008, 12:41 AM

Well, it was a long story behind the amp: BFPR chassis that was hotrodded, put completely back to "stock" and with all new pots, caps etc. & inserted in a SFPR cabinet I'm bummed because the amp does sound great (though the speaker is just a Pro Jr. stock speaker that ain't much), except for the reverb. I bought it as an amp I could just play without getting it immediately serviced because it was just fixed up. Now I'm kinda afraid to play it until I figure this out. Geez, I've played only tube amps for 20+ years and had zero problems until this.

Well, he seemed honest about this whole thing. Maybe something broke in shipment like a lead in the pan or something. I'll see what he says, swap some tubes, and go from there.

Wally · February 4th, 2008, 04:41 PM

V2 is your reverb send tube. I hope you can get it all figured out.
P.S. There is at least one excellent tube amp tech not too far from you...Tim Swartz can get that thing 100% correct.

February 3rd, 2008, 03:30 PM	#1 (permalink)
Stubee Tele-Meister Join Date: Jan 2007 Location: Mid-Michigan Age: 58 Posts: 465	"New" SFPR reverb problem? You guys helped convince me a Princeton Reverb was a good amp, and you were right. Just got a SFPR with BFPR chassis. Very nice overall & the tone is wonderful. Pics later, but a question on the reverb: This has new tubes, caps, reverb tank, but the reverb just doesn't have much "verb". I compared it with my old MusicMan RD112-50 (original reverb tank): The MusicMan reverb on "1" is probably stronger than the Princeton at "10". The SFPR 'verb does change the amp tone when used, but it's a very faint effect The vibrato works fine & strongly. So I looked at the tubes. All amp tubes glow brightly & evenly except for the farthest right (looking at the back of the cab). That one (12AT7?) is barely lit at all; I had to look closely to see if any current is going through it. It's only lighting up the filament at the very end (glass end) of the tube & barely gets warm. I removed the tube, put it back in. It seems to seat well. I've contacted the seller to get his advice, but DK when he'll be able to respond so am asking you guys. Bad tube or do the reverb tubes not draw much current? I did the search & see all the info on bad tank leads, but wonder about this low-glow tube. Any ideas welcome, thanks.

February 3rd, 2008, 03:55 PM	#2 (permalink)
skeksis Tele-Meister Join Date: Dec 2007 Location: phoenix Age: 31 Posts: 399	I'd suggest checking to make sure the new tubes match the tube chart... and trying a different tube in the reverb send/return slots. V1 (furthest right) ought to be a 12ax7 or 7025, V2 a 12at7, V3 12ax7, V4 a 12ax7. if V2 (reverb send) is bad, or maybe V3 (reverb-recovery, which might only be half-bad), you might get the symptom you describe. make sense? __________________ most of the time: '55 LP Jr. or MIJ '62 Custom Tele ----> '08 Marsh 5F4 Super kit http://www.myspace.com/jswattsmusic

February 3rd, 2008, 05:40 PM	#5 (permalink)
Stubee Tele-Meister Join Date: Jan 2007 Location: Mid-Michigan Age: 58 Posts: 465	Update OK: I did a coupla things: Pulled a 12AX7 outta my good little Pro Jr. That tube glows brightly in the Princeton in the V1 port, but didn't add any reverb whatsoever. Didn't have time to mess with other tubes right then. Bumped it a couple of times. Yes, it does "crash", but it is faint and about 5%-10% the noticeable crash ya get when ya bump my MM or the older Fender Reverbs I used to have. It is very faint. Then the seller answered me. He said this may be the amp that he changed the reverb return/mix resistor on because it had too much reverb for his use. He's checking his records so I'll wait to here on that. If that's the case, wish he'd told me. I don't use it much anyway but if it's there, I want it working.

February 3rd, 2008, 06:30 PM	#6 (permalink)
Dacious Friend of Leo's Join Date: Mar 2003 Location: Godzone Posts: 2,623 35 Photos	Try flipping the reverb leads over on the back of the chassis. Oldest trick in the book with a Fender, putting them on the wrong way around. Result is no 'verb. __________________ My other Telecaster is a Thinline The Tele Bible, Ch 1, v 10 Love thy Telecaster, covet not thy neighbour's Strat!

February 3rd, 2008, 03:57 PM	#3 (permalink)
Wally Friend of Leo's Join Date: Mar 2003 Location: Lubbock, TX Posts: 4,212	If the filaments are glowing, I don't think that the problem. Different tubes have different 'visibility' of the filament glow. I am not saying that that tube is good but that I think the filament is not the problem. If you have another 12At7 or even a 12ax7, sub it into that V2 position and see if there is a change. The reverb return is one-half of V3 (12AX7). If the sub into V2 doesn't help, sub into V3. If that doesn't help, the problem lies elsewhere.....tank, reverb transformer, cap, resistor, pot..lots of possibilities. That reverb should get into surf territory. Does the reverb 'crash' when you hit the amp or rock it? If so, the return might be fine and the problem may lie in the send part of the equation. FWIW, I consider it prudent to have a newly acquired amp evaluated by a good tech. Just because it is making sound doesn't mean everything is as it should/could be.

February 3rd, 2008, 05:02 PM	#4 (permalink)
Stubee Tele-Meister Join Date: Jan 2007 Location: Mid-Michigan Age: 58 Posts: 465	The seller numbered the tubes & told me what order to put them in, as he'd removed them for shipment (and packed the amp like a tank). I don't think I have another pre-amp sized tube laying around but will check, I can always get one somewhere. No, it doesn't seem to "crash" like my MusicMan does when bumped a bit but I didn't bump it much to test. As far as filament "glow", let me clarify: I thought this tube was completely out, I could only see any sign of charge when I really stared at the bulb end for a bit, and there sure ain't much there. Play it for 45 minutes, that tube isn't hot but barely even warm. I think the only reason it's even above room temperature is because of the heat from the adjacent "glowing" tubes. I mean, this thing ain't glowing. I'll also look up the schematics on this thing so I understand what tube is doing what (V1 etc.). Arggh...this amp was just completely redone by the previous owner & he sounded like he knew his business. I hope it doesn't need an amp Dr. cuz there ain't one around here & it sounds great except for the 'verb. Thanks much,

February 3rd, 2008, 11:49 PM	#7 (permalink)
Stubee Tele-Meister Join Date: Jan 2007 Location: Mid-Michigan Age: 58 Posts: 465	Dacious: flipped the leads. Result: no difference, though it did seem to take away the very faint "hum" I got with the reverb cranked to 10. Darn, I liked that solution. Well, I'm waiting back to hear from the guy on the "resistor" and will look at the rest of the tubes tomorrow. Thanks,

February 4th, 2008, 12:41 AM	#9 (permalink)
Stubee Tele-Meister Join Date: Jan 2007 Location: Mid-Michigan Age: 58 Posts: 465	Well, it was a long story behind the amp: BFPR chassis that was hotrodded, put completely back to "stock" and with all new pots, caps etc. & inserted in a SFPR cabinet I'm bummed because the amp does sound great (though the speaker is just a Pro Jr. stock speaker that ain't much), except for the reverb. I bought it as an amp I could just play without getting it immediately serviced because it was just fixed up. Now I'm kinda afraid to play it until I figure this out. Geez, I've played only tube amps for 20+ years and had zero problems until this. Well, he seemed honest about this whole thing. Maybe something broke in shipment like a lead in the pan or something. I'll see what he says, swap some tubes, and go from there.

February 4th, 2008, 04:41 PM	#10 (permalink)
Wally Friend of Leo's Join Date: Mar 2003 Location: Lubbock, TX Posts: 4,212	V2 is your reverb send tube. I hope you can get it all figured out. P.S. There is at least one excellent tube amp tech not too far from you...Tim Swartz can get that thing 100% correct.