weak fender 'vibrato'...

[opus]

i've got a SF Bandmaster with a particularly weak 'vibrato' anyone suggestions on how to make it stronger? thanks!

[brad347]

new vibrato tube or if that doesn't work, a new opto "roach"

[opus]

thanks! just did a full retube so... tell me more about this opto 'roach'

as you may or may not be able to tell i'm not going to be doing the work... :rolleyes:

[brad347]

was it weak before you did the re-tube? If not, that would be the first place I would start. "Infant mortality" of new tubes is NOT by any means unheard of. I'd swap it with another in the amp or if you have an extra just to be sure.

The optoisolator "roach" is a component consisting of a neon bulb and a light-dependent resistor (LDR) packaged together in heat-shrink tubing or other such black stuff. You can look at the circuit board and see it... it is the only such component of its type and has four leads coming out of it. Looks kind of 'bug-like,' hence the name.

Sometimes, they do wear out and start getting weak. I've had to replace two in my amps... generally they seem to have a lifespan of 35-40 years.

Four solder joints. Easy job. The part itself is getting a little harder to find... Hoffman used to sell them. I think mojo might have them. A lil on the expensive side (like 20-ish bucks). Good luck!

[Pearly Gator]

Try replacing the tremelo tube's cathode bypass caps. That would be the next thing to check.

Good luck! =)

Gator

[opus]

after taking a look at the tubes, i remembered that only v1, v2, v3 and the power tubes were replaced... that leaves v4 as a possible culprit, which is the phase inverter (?), so v3 should be tremelo? trem was weak before the tube swap, and had also started 'ticking' when it was engaged...

[brad347]

to a certain degree the ticking is normal. If you're getting a strong ticking then the tube is strong.

FWIW, I'd recommend putting your cheapest, most microphonic, oldest, and most generally crappy tube in v3. The vibrato tube is for oscillation only and is not in the signal path. You can save your good tubes for v1 v2 and v4 which are the critical positions. This also cuts down on the ticking which is an inherent flaw in the design unfortunately.

The ticking also indicates that the neon lamp in the opto is pulsing, and therefore it's probably the LDR that is bad. Generally you just replace the whole module.

[doctorx]

Replace the trem roach. I had to do this on my Quad Reverb and Bandmaster and it fixed it.

[Blue Strat]

Use a "surf bug" trem roach. Vintage Jon on the Fender Forum has these.

These are much more consistent than stock trem bugs and every one I've tried give deeper trem. They also have less insertion loss so your normal tone is better as well.

[opus]

hey, thanks for the advice!

[Blue Strat]

Surf Bug http://www.tonecraftamprepair.com/html/surf_bug.html

[doctorx]

I don't want to hurt anyones feelings, but $25 is way too damn much to pay for a lightbulb, a photo resistor, and a 1 inch piece of heatshrink. For that kind of money it would have to be hand delivered by college girls in bikinis.

Ted Weber has one for $7 (https://weberspeakerscom.secure.powweb.com/store/miscord.htm), it's OPT-1 near the bottom of the page.

[Blue Strat]

I don't want to hurt anyones feelings, but $25 is way too damn much to pay for a lightbulb, a photo resistor, and a 1 inch piece of heatshrink. For that kind of money it would have to be hand delivered by college girls in bikinis.

Ted Weber has one for $7 (https://weberspeakerscom.secure.powweb.com/store/miscord.htm), it's OPT-1 near the bottom of the page.

Is it too much if it far exceeds the crappy ones out there? Jeez:jo

[Old Tele man]

"...you gets whats yous pays for..!"

[Jim Salman]

Use a "surf bug" trem roach. Vintage Jon on the Fender Forum has these.

These are much more consistent than stock trem bugs and every one I've tried give deeper trem. They also have less insertion loss so your normal tone is better as well.
I've heard of these before. I'm having some trouble understanding how they can have "less insertion loss" though. I assume you mean that, when the bulb is not lit, the photocell has a higher resistance than the ones normally found in Fender trem opto-isololators. So maybe the resistance (with no light) is, say, 20 Megohm instead of 10 Megohm. But the real tone sucker in this type of trem circuit is the 50K-RA intensity pot. This pot is wired so that it presents a 50K load to ground directly on the preamp signal. Even at high or maximum settings of the intensity knob (the wiper is connected to one side of the photocell, the other side of the photocell is grounded) the 10 Meg+ parallel resistance of the dark photocell will hardly matter.

Or am I missing something here?

[doctorx]

I've heard of these before. I'm having some trouble understanding how they can have "less insertion loss" though. I assume you mean that, when the bulb is not lit, the photocell has a higher resistance than the ones normally found in Fender trem opto-isololators. So maybe the resistance (with no light) is, say, 20 Megohm instead of 10 Megohm. But the real tone sucker in this type of trem circuit is the 50K-RA intensity pot. This pot is wired so that it presents a 50K load to ground directly on the preamp signal. Even at high or maximum settings of the intensity knob (the wiper is connected to one side of the photocell, the other side of the photocell is grounded) the 10 Meg+ parallel resistance of the dark photocell will hardly matter.

Or am I missing something here?

Agreed, and if you replace that pot with one with a switch you can remove it and the tone sucking with a click, then back in again when you need it. Install that and Teds seven dollar so called "crappy" trem roach (Sorry Mike) and yer in bizness. You can get the pot w/switch from ted for a couple of dollars too.

Regarding trem roaches, not trying to start a flame war, but do you think Leo paid $25 a pop or its sixties equivalent for trem roaches back in the day? I don't think so. How many thousands, or tens of thousands of Fender amps from the sixties and seventies are out there right now with great sounding tremolos?

[DGG]

Is it too much if it far exceeds the crappy ones out there? Jeez:jo

I mean VJon actually builds them by hand, tests them under HIGH voltage (typical operating conditions) and makes sure they are up to his standards for thick modulation.

But, someone who takes the time research, build and test EACH unit isn't worth being paid $25?! You build a superior, high-quality product and yet the public wants it for free? It's an American researched and hand-made product by someone having to pay incredible dues to get that product to the masses and it's still not cheap enough @$25.

Vintage Jon ought to charge $50 IMO. That's really what those "Surf Bugs" are worth. I've used them myself in my personal amps and installed them in other's amps and they never thought they were getting ripped off for $25 for the part. The smile on their face when they use theat trem lasts for years.

[DGG]

How many thousands, or tens of thousands of Fender amps from the sixties and seventies are out there right now with great sounding tremolos?

Uh, I've serviced some with lowsy stock trems. It's a reality they do go bad.

[mbratch]

So, opus, did replacing the opto-coupler fix the weak vibrato?

[Angle Loss]

I mean VJon actually builds them by hand, tests them under HIGH voltage (typical operating conditions) and makes sure they are up to his standards for thick modulation.

But, someone who takes the time research, build and test EACH unit isn't worth being paid $25?! You build a superior, high-quality product and yet the public wants it for free? It's an American researched and hand-made product by someone having to pay incredible dues to get that product to the masses and it's still not cheap enough @$25.

Vintage Jon ought to charge $50 IMO. That's really what those "Surf Bugs" are worth. I've used them myself in my personal amps and installed them in other's amps and they never thought they were getting ripped off for $25 for the part. The smile on their face when they use theat trem lasts for years.


I installed one on a friend's BF Bandmaster. It was kinda expensive for a small part, but what an incredible difference it made. The tremelo afterwards sound good and was able to get very deep. I'm considering purchasing one for my '66 Super Reverb. I'd love to hear more discussion of the technical aspects of the classic opto tremelo. I'm enjoying this thread.

[opus]

ah, i've just got my amp back from my tech so i've been reluctant to give it up again (i think i just found out what is sounds like when a speaker has broken in :D)

i'm going to be out of town next week so hopefully he can get it done while i'm gone. i'll post a report when it's done, thanks again for the suggestions!

i'd like to be doing this stuff myself at some point, i've only soldered speaker leads up to this point. i need a good starter project...

[brad347]

i need a good starter project...

Build a fuzz face clone! Check out www.generalguitargadgets.com

Good luck with that tremolo.

[mbratch]

My BFDR suddenly went weak in vibrato land. Used to have it set to about 5 or 6 on intensity for a deep vib, now I have to set it to 10. Vib is now very subtle at 5.

I bought a new opto-isolator and it still sounds the same. Different 12AX7, same. What else can make the vib/trem weak?

[brad347]

perhaps a resistor has drifted up, or your intensity pot is dirty? There are those 3 ceramic disc caps in the oscillator circuit too... they mainly affect the degree of phase shift of the oscillator but if one developed a high DC resistance, who knows what would happen? I'm just shooting in the dark here.

[mbratch]

Thanks. I did replace the 1M resistor (it had drifted to 1.3M) with one that was around .94M, but that didn't change anything. I am only partially knowledgeable on the theory of operation of the "vibrato" circuit, so some of those items are a shot in the dark for me, too. The caps and other resistors are easy to check of course, so I'll just run through them.

All this is of course assuming the vibrato should be pretty strong on intensity 5. Is that the case?

[brad347]

it will be audible but not stuttery.

[mbratch]

Thanks Brad... I went back to listen more intently. What I'm finding is that it becomes just (and I mean *just*) perceptible at about 4 on the intensity dial. Oh... forgot to mention I had already cleaned the pots.

Hey, do you own an ES-347? Or is that number in your name just a coincidence. :)

[brad347]

I do indeed own an ES-347. 1984 in cherry finish (red) which is pretty rare for that model. Mine is the later version with teh stop tailpiece (instead of TP-6) and the mini-toggle for the coil-tap (instead of the second full-size toggle on the earlier models).

I love it... it was my main guitar for a long time and it's still the guitar I take when i'm not sure what the gig will be like stylistically. It will be fine on just about any gig... very versatile. But it's not the go-to #1 for anything in my lineup right now. Of course that, too, will probably change :)

Sorry for the off-topic, thanks for asking :D

[mbratch]

OK, I get one OT as well just to make it fair and that's it. :)

I also own one, a 1981 tobacco burst wit hthe TP-6 and old coil tap switch. I didn't care much for the stock pickups and put in Harmonic Design Classic HBs. It sounds awesome full as well as tapped. Almost P90-ish tapped. I use it for jazzy comps, then click it on full for fat, jazzy leads. BTW, I like the tunes on your site. I don't play jazz really, but wish I could and sometimes I pretend. :)

Back to the tremolo (er... Leo's "vibrato"), anyone know if what I'm describing sounds normal? I didn't think it was because I believe it was stronger before, but looking for validation.

[opus]

so i've had too many rehersals, etc. lately to take the amp in so i've not had the vibrato worked on yet..., i thought i'd ask another question though...

when the vibrato is engaged with the footswitch there is a slight delay before it kicks in..., the only other BF/SF fender amp i had did not have this problem. anyone have any suggestions? all the help is greatly appreciated.

[opus]

just an update for anyone remotely interested..., i finally got my amp back in the shop, i ordered a surf bug, had it installed and had my tech do the vibrato slow-down and tick-fix detailed here:

http://www.regiscoyne.com/tech/tremolo/

the surf bug is awesome, definitely deeper than before (jury is still out on whether it is better than other BF amps I've had..., can't do a side by side), very deep, musical tremelo, having the speed slowed down gives me a much more useable range, anyone else have this done?

thanks for the suggestions, comments.

[mbratch]

I did the slow-down mod on my gigging amps and I like the results.