Nice video! Appreciate your attention to detail about some subtle changes in the circuit. Most people miss those. That's why I'm posting this additional information. You seem like the kind of guy who would care. :-) The reason your faceplate came loose on that end is because you are missing a Fender installed retaining piece on the jewel assembly. As others have mentioned, on these amps there was a chrome flange washer that screwed UNDER the jewel itself, but OVER the faceplate. This is what holds the faceplate secure on that end, not just adhesive. These flange washers were often lost because people forget to put them back on when replacing the jewel lamps. I would be glad to post a photograph of this oft-forgotten Fender part, which I can show as original to my late 1973 mfg. date Vibrosonic Reverb. This trim washer was actually a kludge introduced by Fender by about early 1973. 1972-74 Sales literature does not show the flange washer on the sample amps. The faceplates were coming loose due to the heat of the power supply softening up the adhesive. I have seen many Fender amps with this washer still in place, but many more with it missing. It is easy to lose. But why the kludge? There is a reason and here it is. FWIW, the 100W amp series faceplates were made independently and easily removable by non-assembly technicians at Fender. This was accomplished by keeping them clear of most front panel potentiometer retaining nuts and the jewel assembly. The holes were simply punched out larger. Only the input jacks and brite switches were encumbered. This was on purpose. This was to allow Fender to accomplish final branding on the chassis at a much later point in production. That was done because this one chassis design, aka "100W RMS amp with reverb and Vibrato" was used for no less than FIVE otherwise electrically identical Fender amplifiers. Those were the Quad Reverb, The Super Six, the Vibrosonic Reverb, the Dual Showman Reverb and the Twin Reverb. Thus, Fender could build a single line of amplifiers to 95% completion, and brand them via faceplate at the very last moment based on demand, and with only very minimal technical intervention, and NO SOLDER WORK required. This vastly shortened delivery time and allowed Fender to respond to market demand, instead of having to have five lines in parallel, or rotate production through multiple versions, or end up with unwanted back stock of less popular models because of bad sales projections. Note too that this amplifer series came either with or without a pull boost option from the very beginning. Fender did not "add that later". Schematic, here; www.bustedgear.com/images/schematics/Fender_100W_SF.pdf All these details can be confirmed from the schematic, including the "pull boost option" See note 5 on the schematic, where Fender specifically states that pull boost was "used in some versions". The pull boost option was original to this design, and debuted in 1972, which is confirmed by Fender sales literature of the period. Read Page 49, here; www.dropbox.com/s/6fo2m2lulce5a58/1972%20Fender%20Catalog.pdf?dl=0 FWIW, my late 1973 mfg. date Vibrosonic has this feature. It is easy to find example both with and without pull boost dating to this period, so it was not a "later addition" by Fender. It was there from the beginning of this design, as both the catalogue information and well dated examples still extant easily demonstrate. I have never been able to discover how one could get this design amp WITHOUT pull boost. Perhaps Fender simply did not include this feature on a set number of amps? Perhaps it happened due to a lack of parts availability, or by special order, or for export only? I can find now compelling explanation, nor logic to the thing. But they definitely did it and examples of both are easily discoverable. Cheers to you!
Different amp than the original brownface Vibrasonic. That was a beefed up PRO from around 1960, complete with a bigger OT and a 15" LBJ as we used to call 'em. As a guitar player (not a repair guy), I really appreciate you making such effort to make this amp right!!
Another great and helpful video! I have an early 70s Fender TFL5005D Bandmaster. Added a trim pot to the existing Bias Balance Pot. Nice to be able to balance the output tubes and set the bias as well. Good stuff. Oh, please keep an eye on the weather in your area for Wednesday March 30. You are under a Moderate Risk for a severe weather outbreak. Things could get crazy with the weather around there. Stay Safe!
The hits keep coming! Thanks for the video, Lyle. Just as an aside, I have a similar era Twin Reverb in my shop right now and it has a large chrome finish washer between the jewel light and the front panel. Not sure where you might find an aftermarket replacement, but it looks like that's how it was done.
@@PsionicAudio I found an M18x22x1.5 aluminum washer (think auto oil drain washer) works OK. It’s a tad oversize but with a heat shrink shim fit well. Not perfect but easy and inexpensive.
I've heard people criticize the push-pull circuit before, but I've never really understood why. I have a 1980 Princeton Reverb with that feature. I bought it new back in '80 or '81. It sounded kinda bleh when I first got it, but I put a Weber speaker in it and now it's the best-sounding amp I've ever owned.
Hi Psionic! Love your videos... I don't know if any Fender 400PS bass amps pass through your shop, but I'd love to see you repair one these. I'm rebuilding a couple of these amps, and I think the output section could be done better. The output section has some rather large grid snubber caps that probably take out a lot of treble frequecies. Also, I don't quite understand the logic behind the bass input cathode caps being of smaller value than the normal channel's cathode caps. Anyway, thanks again for the videos, you have a very informative channel.
Echoing an earlier comment, these Silverface amps had a trim-ring to hold faceplate down, held by the jewel light. You can see the scratch on the faceplate where it once was.
I have a 69 Bandmaster Rev on the bench right now that I couldn't get the bias any hotter than 45% and when I started bringing the resistor down, the plate voltage was just in the basement at like 355v....poor thing looked like it sat on a shelf next to a turbo 350 transmission in a garage for 40 years, plugged in and on, when I first got it in.
I own a 1976 one of these. They are as rare as hen's teeth here in the UK. Mine had a JBL d130 speaker that I changed for a eminence legend 15". It is a great amp that I would never sell.
@@jonnybeck6723 it is a orange one and needed to be re coned. I am planning on re coning it and putting it back in , though the Legend is an amazing speaker for Fenders. I don't think the d130 would be any better! I also used a 12" legend in my 5e3 I built. Killer tones from that!
@@PsionicAudio I took the pull boost off of mine because the switch fell apart and they are difficult to get in the UK. The boost was a crappy design and didn't much anyhow.
Great video....my '73 Pro Reverb (non master volume) has only 5 25/25 bypass caps on the board with one of them being a 5/50. Yet all the silverface circuits I 've seen have 7 caps? They are the old white original mallory caps which need changing. Just wondering if i should add the extra 2 caps as per all the circuits I've seen? And would a 25uf/50volt cap be ok to replace the 5/25 cap?
I have seen that oversized coupling cap in silver face Deluxe Reverbs as well. The stock DR speaker won't like it and many replacement speakers will not like it either, and if you do have a speaker that will handle it it will literally make your pants leg flap if you stand close to the amp. You will get more headroom from the amp if you change that coupling cap back to the earlier blackface value.
@@PsionicAudio My dusty memory seems to recall getting a thin chrome washer from Ace Hardware that worked after I. Opened the hole up a bit with a Dremel sanding bit.
@@PsionicAudio So, if I understand you correctly, you are saying that the hole in the silkscreened trimplate is larger than the typical bezeled/beveled nut/collar assembly used on other Fender pilot lights? How large is the hole in the trimplate? I may have parts that'll fit and look "stock"....
@@NoOne-sn2si , interestingly, I have some vintage DialCo brand bayonet sockets that have a very slightly larger outer flange/bezel than the Fender flanges, 13/16" diameter instead of 3/4" (aka12/16). I don't know if that's big enough however to catch the cosmetic trim plate and hold it down. The DialCo sockets accept the same screw-in "jewel" as the Fender sockets and would look the same from the outside, but they are self-contained cylinders, a little like a stubby vintage bakelite fuse holder, not open frame like the Fender sockets. They can be kind of expensive on the vintage market, anywhere from $8 to $30 !! and they come in two varieties, one for use with an ordinary #47 incandescent bulb, and another with same bayonet socket but including a built-in resistor so that you can run a 120VAC neon lamp. Obviously they're not interchangeable and the DialCo socket with the built-in resistor won't work for a 6-volt incandescent bulb, and there's no part number on them to differentiate the two types! (Check them with a multimeter). They might be a drop-in fit in place of a Fender lamp socket (if length allows); or, the integral (crimped on) 13/16" metal collar could be cut off with a Dremel tool and used with the standard open-frame Fender socket, *if* the fractionally larger flange will work to hold the trimplate down..... I had a repartee' with guitarist Tab Benoit about fractions last week; he was telling the audience that he's been using pandemic downtime to repair storm damage to his home and bayou camp, but he's not good with fractions and so his reconstruction efforts never seem to go smoothly. He chuckled when I pointed out that most plywood isn't 1/2" these days, it's 29/64ths!
Hey-oh Lyle... are your Strat pickups and electronics stock (?) ...and in your opinion are PPIMV's really worth the geek/nerd lust? Thanx for another cool vid and... Cheerios (but not for breakfast)
No, not stock. I have videos up on the pickups and mods. This was my Psionic Egobooster (musikraft partscaster). The strat with rosewood board, Gotoh 510, Suhr Thornbucker and Mojotone '67 Quiet Coils and non-standard wiring (I can do series/parallel on the bridge and blend in the neck pickup).
I rip out the boost circuit and restore the reverb stuff to AB763. That just leaves the MV itself. At which point I remove the bright cap on the MV and it sounds good again.
I think the people at Fender were doing too much Orange Sunshine in the 70's... Some of their engineering/manufacturing choices were, um, hard to understand...
![[Sub Thai] APT. - ROSÉ & Bruno Mars](http://i.ytimg.com/vi/bYjhzP8x_uc/mqdefault.jpg)
Nice video! Appreciate your attention to detail about some subtle changes in the circuit. Most people miss those. That's why I'm posting this additional information. You seem like the kind of guy who would care. :-) The reason your faceplate came loose on that end is because you are missing a Fender installed retaining piece on the jewel assembly. As others have mentioned, on these amps there was a chrome flange washer that screwed UNDER the jewel itself, but OVER the faceplate. This is what holds the faceplate secure on that end, not just adhesive. These flange washers were often lost because people forget to put them back on when replacing the jewel lamps. I would be glad to post a photograph of this oft-forgotten Fender part, which I can show as original to my late 1973 mfg. date Vibrosonic Reverb. This trim washer was actually a kludge introduced by Fender by about early 1973. 1972-74 Sales literature does not show the flange washer on the sample amps. The faceplates were coming loose due to the heat of the power supply softening up the adhesive. I have seen many Fender amps with this washer still in place, but many more with it missing. It is easy to lose.
But why the kludge? There is a reason and here it is.
FWIW, the 100W amp series faceplates were made independently and easily removable by non-assembly technicians at Fender. This was accomplished by keeping them clear of most front panel potentiometer retaining nuts and the jewel assembly. The holes were simply punched out larger. Only the input jacks and brite switches were encumbered. This was on purpose. This was to allow Fender to accomplish final branding on the chassis at a much later point in production. That was done because this one chassis design, aka "100W RMS amp with reverb and Vibrato" was used for no less than FIVE otherwise electrically identical Fender amplifiers. Those were the Quad Reverb, The Super Six, the Vibrosonic Reverb, the Dual Showman Reverb and the Twin Reverb. Thus, Fender could build a single line of amplifiers to 95% completion, and brand them via faceplate at the very last moment based on demand, and with only very minimal technical intervention, and NO SOLDER WORK required. This vastly shortened delivery time and allowed Fender to respond to market demand, instead of having to have five lines in parallel, or rotate production through multiple versions, or end up with unwanted back stock of less popular models because of bad sales projections.
Note too that this amplifer series came either with or without a pull boost option from the very beginning. Fender did not "add that later". Schematic, here; www.bustedgear.com/images/schematics/Fender_100W_SF.pdf All these details can be confirmed from the schematic, including the "pull boost option" See note 5 on the schematic, where Fender specifically states that pull boost was "used in some versions". The pull boost option was original to this design, and debuted in 1972, which is confirmed by Fender sales literature of the period. Read Page 49, here; www.dropbox.com/s/6fo2m2lulce5a58/1972%20Fender%20Catalog.pdf?dl=0 FWIW, my late 1973 mfg. date Vibrosonic has this feature. It is easy to find example both with and without pull boost dating to this period, so it was not a "later addition" by Fender. It was there from the beginning of this design, as both the catalogue information and well dated examples still extant easily demonstrate.
I have never been able to discover how one could get this design amp WITHOUT pull boost. Perhaps Fender simply did not include this feature on a set number of amps? Perhaps it happened due to a lack of parts availability, or by special order, or for export only? I can find now compelling explanation, nor logic to the thing. But they definitely did it and examples of both are easily discoverable.
Cheers to you!
My Vibrosonic has factory washer on the jewel light. It must have been lost/replaced on this one.
Different amp than the original brownface Vibrasonic. That was a beefed up PRO from around 1960, complete with a bigger OT and a 15" LBJ as we used to call 'em. As a guitar player (not a repair guy), I really appreciate you making such effort to make this amp right!!
That is a nice sounding amp imo. Thanks Lyle! Excellent work as always.
Glad you like it!
Nice explanation and demo. Thanks for the detail on the coupling cap. I’ve chased a few ghosts on that one...
Another great and helpful video! I have an early 70s Fender TFL5005D Bandmaster. Added a trim pot to the existing Bias Balance Pot. Nice to be able to balance the output tubes and set the bias as well. Good stuff. Oh, please keep an eye on the weather in your area for Wednesday March 30. You are under a Moderate Risk for a severe weather outbreak. Things could get crazy with the weather around there. Stay Safe!
Nice job and sweet updates.
The hits keep coming! Thanks for the video, Lyle. Just as an aside, I have a similar era Twin Reverb in my shop right now and it has a large chrome finish washer between the jewel light and the front panel. Not sure where you might find an aftermarket replacement, but it looks like that's how it was done.
Yeah, but so so many amps have them missing.
@@PsionicAudio I found an M18x22x1.5 aluminum washer (think auto oil drain washer) works OK. It’s a tad oversize but with a heat shrink shim fit well. Not perfect but easy and inexpensive.
Nice work on the faceplate. I've got a recently acquired 74 Super Reverb and an ultralinear Pro Reverb that need the same treatment.
I've heard people criticize the push-pull circuit before, but I've never really understood why. I have a 1980 Princeton Reverb with that feature. I bought it new back in '80 or '81. It sounded kinda bleh when I first got it, but I put a Weber speaker in it and now it's the best-sounding amp I've ever owned.
The PR push-pull boost circuit is totally different from the later sf Pro and Twin push-pulls.
nothing sweeter than a strat into a silverface
Hi Psionic! Love your videos... I don't know if any Fender 400PS bass amps pass through your shop, but I'd love to see you repair one these. I'm rebuilding a couple of these amps, and I think the output section could be done better. The output section has some rather large grid snubber caps that probably take out a lot of treble frequecies. Also, I don't quite understand the logic behind the bass input cathode caps being of smaller value than the normal channel's cathode caps.
Anyway, thanks again for the videos, you have a very informative channel.
Echoing an earlier comment, these Silverface amps had a trim-ring to hold faceplate down, held by the jewel light. You can see the scratch on the faceplate where it once was.
Yeah, but they are very commonly lost. And nothing (even on special hardware sites) is a good replacement
I have a 69 Bandmaster Rev on the bench right now that I couldn't get the bias any hotter than 45% and when I started bringing the resistor down, the plate voltage was just in the basement at like 355v....poor thing looked like it sat on a shelf next to a turbo 350 transmission in a garage for 40 years, plugged in and on, when I first got it in.
The oils in the GooGone will make it very difficult for new glue to adhere to the metal. You need to clean that stuff off REALLY good before gluing.
Yeah, I have naptha for that.
did I miss mention of valve availbility - or is that for future video ?
Soon but not yet. I'm primarily a working tech not a TH-cam content creator, so as I have time. Crazy busy right now.
I own a 1976 one of these. They are as rare as hen's teeth here in the UK. Mine had a JBL d130 speaker that I changed for a eminence legend 15". It is a great amp that I would never sell.
Why did you swap out the D130? (and was it grey or orange?)
Cheerios
Electronically it's a Twin Reverb. Haven't looked to see if it's the same OT but I suspect it is. Same amp, different cabs/speakers, different name.
Scored one just a couple of weeks ago here in NI. Splendid amp, though mine came with non-original Black Widow speaker.
@@jonnybeck6723 it is a orange one and needed to be re coned. I am planning on re coning it and putting it back in , though the Legend is an amazing speaker for Fenders. I don't think the d130 would be any better! I also used a 12" legend in my 5e3 I built. Killer tones from that!
@@PsionicAudio I took the pull boost off of mine because the switch fell apart and they are difficult to get in the UK. The boost was a crappy design and didn't much anyhow.
Great video....my '73 Pro Reverb (non master volume) has only 5 25/25 bypass caps on the board with one of them being a 5/50. Yet all the silverface circuits I 've seen have 7 caps? They are the old white original mallory caps which need changing. Just wondering if i should add the extra 2 caps as per all the circuits I've seen? And would a 25uf/50volt cap be ok to replace the 5/25 cap?
The 5/50 is better. And look over by the RCA jacks for the other two caps. They’ll be there.
@@PsionicAudio Thank you. There is an extra one on the vibrato rca which makes 6 in total. No sign of a 7th cap
Huge fan of 15" speaker Fenders!
authentic lick.......
I'm going to ask my wife for one of those...... and I will accept no knock-offs or substitutions!😁
Do you have an output voltage reading for the main transformer. I bought one with a busted/burned transformer.
It’s the same PT as a Twin Reverb.
I have seen that oversized coupling cap in silver face Deluxe Reverbs as well. The stock DR speaker won't like it and many replacement speakers will not like it either, and if you do have a speaker that will handle it it will literally make your pants leg flap if you stand close to the amp. You will get more headroom from the amp if you change that coupling cap back to the earlier blackface value.
You don't want the 1nF if the amp has the 330K grid leaks. 3.3nF for those gives the AB763 response.
@@PsionicAudio do you think it was a design thing meant for pedal steel players? who apparently this amp was meant for
What is your opinion on ”blackfacing”? The only thing I would change in my SFVR is the amount of bass. (The bias balance has been changed already.)
Oh, you addressed some of those in the video 🤦♂️
There should be a big shiny washer under the jewel to hold the faceplate down.
I agree. But they have gone missing on so many SF amps that come in. And I haven't found a source for a suitable replacement (McMaster, etc).
@@PsionicAudio My dusty memory seems to recall getting a thin chrome washer from Ace Hardware that worked after I. Opened the hole up a bit with a Dremel sanding bit.
@@PsionicAudio So, if I understand you correctly, you are saying that the hole in the silkscreened trimplate is larger than the typical bezeled/beveled nut/collar assembly used on other Fender pilot lights? How large is the hole in the trimplate? I may have parts that'll fit and look "stock"....
@@goodun2974
Yes, it's bigger than the light bezel. The faceplate hole on mine is 3/4" and I'm missing the washer...
@@NoOne-sn2si , interestingly, I have some vintage DialCo brand bayonet sockets that have a very slightly larger outer flange/bezel than the Fender flanges, 13/16" diameter instead of 3/4" (aka12/16). I don't know if that's big enough however to catch the cosmetic trim plate and hold it down. The DialCo sockets accept the same screw-in "jewel" as the Fender sockets and would look the same from the outside, but they are self-contained cylinders, a little like a stubby vintage bakelite fuse holder, not open frame like the Fender sockets. They can be kind of expensive on the vintage market, anywhere from $8 to $30 !! and they come in two varieties, one for use with an ordinary #47 incandescent bulb, and another with same bayonet socket but including a built-in resistor so that you can run a 120VAC neon lamp. Obviously they're not interchangeable and the DialCo socket with the built-in resistor won't work for a 6-volt incandescent bulb, and there's no part number on them to differentiate the two types! (Check them with a multimeter). They might be a drop-in fit in place of a Fender lamp socket (if length allows); or, the integral (crimped on) 13/16" metal collar could be cut off with a Dremel tool and used with the standard open-frame Fender socket, *if* the fractionally larger flange will work to hold the trimplate down.....
I had a repartee' with guitarist Tab Benoit about fractions last week; he was telling the audience that he's been using pandemic downtime to repair storm damage to his home and bayou camp, but he's not good with fractions and so his reconstruction efforts never seem to go smoothly. He chuckled when I pointed out that most plywood isn't 1/2" these days, it's 29/64ths!
Hey-oh Lyle... are your Strat pickups and electronics stock (?)
...and in your opinion are PPIMV's really worth the geek/nerd lust?
Thanx for another cool vid and...
Cheerios (but not for breakfast)
No, not stock. I have videos up on the pickups and mods. This was my Psionic Egobooster (musikraft partscaster). The strat with rosewood board, Gotoh 510, Suhr Thornbucker and Mojotone '67 Quiet Coils and non-standard wiring (I can do series/parallel on the bridge and blend in the neck pickup).
Oh, and PPIMVs are better but in an amp that's primarily clean like this the pre-PI can be fine.
I restored a 75 champ but the panel is shot can i get a replacement ive looked and so far nothing anybody know?
Lyle cutting loose; he's on a bender !
is there anything that can be done to make the push pull function useable?
I rip out the boost circuit and restore the reverb stuff to AB763. That just leaves the MV itself. At which point I remove the bright cap on the MV and it sounds good again.
@@PsionicAudio thank you, it's on a princeton reverb and i hate it
@@glennbeeler3312 There's another guy commenting here who has one of those and he said it's the best sounding amp hes ever owned......🤔
@@goodun2974 It likely is, long as he don't tug on the reverb knob. @bevo65 didn't say...
👍
I think the people at Fender were doing too much Orange Sunshine in the 70's... Some of their engineering/manufacturing choices were, um, hard to understand...
IKR! Window Pain or Purple Haze!LOL.
Considering what the CVS engineers did to the sound of the classic amplifiers, I think they were doing Blah-ter Acid!
@@goodun2974 I see what ya did there...;)