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Thread: 1964 BF Tremolux With Mods - Anyone know what they are for?

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    1964 BF Tremolux With Mods - Anyone know what they are for?

    Salutations everyone.

    I inherited a 64 BF Tremolux and it was missing the back cover and the vibrato bright switch, looks a little rough but works great.

    After I ordered a new back cover and with the chassis out, I installed a new bright switch, I looked at other Tremolux Amps online and discovered this amp has some radical mods.

    Can you guys comment about this amp? I am not a pro musician, so I would like to know if someone was out of their mind here.







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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Quote Originally Posted by Garity View Post
    Salutations everyone.

    I inherited a 64 BF Tremolux and it was missing the back cover and the vibrato bright switch, looks a little rough but works great.

    After I ordered a new back cover and with the chassis out, I installed a new bright switch, I looked at other Tremolux Amps online and discovered this amp has some radical mods.

    Can you guys comment about this amp? I am not a pro musician, so I would like to know if someone was out of their mind here.






    My spatial orientation is screwed up. More detailed pictures might help in terms of mods.
    Last edited by vinyl; 08-13-2020 at 08:53 AM.

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Maybe these will help. I can understand the power transformer needing to be beefed up for additional tubes, but there are no markings on it. Maybe someone recognizes it as being such and such.


    1965 Tremolux chassis


    My 1964 Tremolux chassis with mods




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    Forum Member DanTheBluesMan's Avatar
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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    good gravy. I'm inclined to think some mad scientist who was thrown out of amplifier university concocted his revenge on that poor tremolux. I have no idea what's what in that rat nest of wiring and what did they do to the rectifier tube?

    welcome to the forum and what an entrance !!
    "Live and learn and flip the burns"

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    The Rectifier Tube was bypassed using 4 diodes configured into a bridge rectifier circuit. Not sure that that would affect the sound though, (I could be wrong), since it just supplies the power for everything else. Rectifier circuits convert the AC input from the plug into DC for the remaining circuitry. I get that part.

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    My WAG, and it's purely a guess, is someone tried to turn it into a twin reverb. Extra tubes, phono jacks, transformer, potentiometer. What a shame.

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    I didn't know exactly how twin reverb differs from single reverb then I discovered it is a model name! Thank you vinyl. It couldn't be a Twin Reverb, those have four 6L6 tubes, but it could have been converted into Vibroverb or Superverb circuitry, I found that here. https://robrobinette.com/AB763_Model_Differences.htm

    You would think that this is bad enough to do to this amp but the ugliness gets worse.







    This was a blonde Tremolux?

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    Forum Member CoyotesGator's Avatar
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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    The freakin’ horror.

    Weird combination of destructive mods and preservation of the blue molded caps.

    You say it sounds good?

    Loaded and unloaded voltages along with measurements of the PT’s physical size might point you towards its manufacturer.

    I’ll bet it is a Triad.

    Fits the hole, clue.

    Welcome!

    What happend?
    Who let the magic smoke out?

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Thanks CoyoteGator, looking at Triad brand transformers, they do look like that brand. Still have not located the same one yet.

    The Rectifier circuit is a full wave, not a bridge. When building Frankenstien amps always use six diodes when two will suffice.






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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    By all means "school" us on rectifiers.

    I await your next "nugget" of info.

    Probably will get me suspended again.

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Quote Originally Posted by vinyl View Post
    By all means "school" us on rectifiers.

    I await your next "nugget" of info.

    Probably will get me suspended again.


    You’re such a cuddly one.

    Do you stick thumb tacks under your toenails on slow days?
    What happend?
    Who let the magic smoke out?

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Quote Originally Posted by CoyotesGator View Post
    You’re such a cuddly one.

    Do you stick thumb tacks under your toenails on slow days?
    I've been called a lot of things, but never cuddly. Obtuse, obstinate, obstreporous maybe.

    Quote Originally Posted by Garity View Post
    The Rectifier Tube was bypassed using 4 diodes configured into a bridge rectifier circuit. Not sure that that would affect the sound though, (I could be wrong), since it just supplies the power for everything else. Rectifier circuits convert the AC input from the plug into DC for the remaining circuitry. I get that part.
    In this post he says there are 4 diodes.

    Quote Originally Posted by Garity View Post
    Thanks CoyoteGator, looking at Triad brand transformers, they do look like that brand. Still have not located the same one yet.

    The Rectifier circuit is a full wave, not a bridge. When building Frankenstien amps always use six diodes when two will suffice.
    In this post there are 6 diodes. There is a reason why there are multiple diodes in series.

    My observations from his not very good pictures.

    1. Indeed, a solid state rectifier is employed.
    2 The octal socket that originally held the tube rectifier has been replaced, as evidenced by the different mounting screws. This socket appears to have a screen grid resistor.

    3. The "additional" octal socket that now doesn't seem to do anything, except hold a "spare" 6L6, also appears to have a screen grid resistor.

    4.The bias power supply cap appears to be original. Can't tell for sure, but there will be a date code on it.

    As to the power transformer, without markings we'll probably never really know.

    Like I said before, more detailed pictures, but that may not help either.

    Pictures under the "doghouse" would be useful.

    Lastly, I have nothing against Garity or CoyotesGator, just a low tolerance for inaccurate info.

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    Forum Member CoyotesGator's Avatar
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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Quote Originally Posted by vinyl View Post
    I've been called a lot of things, but never cuddly. Obtuse, obstinate, obstreporous maybe.



    In this post he says there are 4 diodes.


    In this post there are 6 diodes. There is a reason why there are multiple diodes in series.

    My observations from his not very good pictures.

    1. Indeed, a solid state rectifier is employed.
    2 The octal socket that originally held the tube rectifier has been replaced, as evidenced by the different mounting screws. This socket appears to have a screen grid resistor.

    3. The "additional" octal socket that now doesn't seem to do anything, except hold a "spare" 6L6, also appears to have a screen grid resistor.

    4.The bias power supply cap appears to be original. Can't tell for sure, but there will be a date code on it.

    As to the power transformer, without markings we'll probably never really know.

    Like I said before, more detailed pictures, but that may not help either.

    Pictures under the "doghouse" would be useful.

    Lastly, I have nothing against Garity or CoyotesGator, just a low tolerance for inaccurate info.

    Where exactly are the inaccuracies in my comments?

    Was I incorrect in your preference for hugs?
    What happend?
    Who let the magic smoke out?

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    I did not come here to school you, I came here for you guys to school me. I did not know much about Fender amps when I started posting, but you guys helped me out enough to know enough about this particular one.

    I'm sorry for assuming it was a bridge rectifier at first glance. I do that when I see multiple diodes by the power supply.

    If the diodes in series are protection scheme then you could have just said so, I won't be offended, I just want to understand what happened here.

    I will post the requested doghouse picture later. The caps have been replaced at some point;

    My next question to you guys is what would you do if this was your amp? I do not need an amp and was wondering if it should be restored somehow or just sell it as is and what would a be a fair price for it? I would not have wanted to sell this amp as a tremolux as I would have if I did not take time to look inside. Thanks again for your help.

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    @Garity

    It sounds good on both channels and makes good power?
    What happend?
    Who let the magic smoke out?

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    After running through the functions, Yes, it goes way way too loud for me and all four input jacks work. The bass and treble work for both the Normal and Vibrato inputs. The Bright switches work. To my ear, I like the Vibrato tone better than the Normal tone

    More bad news though, I could not get the Intensity and Speed Pots to affect any change to the Vibrato tone at all.

    Here are the Doghouse caps.






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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Quote Originally Posted by Garity View Post

    More bad news though, I could not get the Intensity and Speed Pots to affect any change to the Vibrato tone at all.
    The vibrato won't work without a footswitch, or shorting plug plugged into the footswitch jack. If you just want to test it you can use a clip lead while it's out of the cabinet to ground the center pin of the footswitch jack.

    Some of the doghouse caps show signs of "bulging", which means they're trying to vent. Could be because they're old, or the voltage across them is in excess of 450 volts DC.

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    The voltages across those doghouse caps read as high as 456 volts when powering up then the highest one stabilized at 305 volts after about 10 seconds.

    Are F&T 22 microfarads 500V suitable replacements? or the 16 microfarads a better choice? The bulging doghouse caps are currently Mallory 20 microfarads 450V.

    I suppose since those are bad I might as well replace the cathode bypass caps too. I understand to keep the blue molded caps. Do you have a suggestion for the capacitor brand for those and the power supply filter cap?

    Also, Thanks for the shorting out the Vibrato pedal knowledge you are awesome! However, no luck on getting it to work. I traced the circuit around through the pots down to the optoisolator, to ensure wire continuity and swapped the tubes around. The optoisolator bulb read 7600 ohms. Is that normal? I will also order the .01 and .02 ceramic caps.

    Any tips about the optoisolator if I order the one for a tremolux from amprepairparts.com? That should be the correct type?

    Thanks again vinyl for the help, I really want someone to have a decent amp.




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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Quote Originally Posted by Garity View Post
    The voltages across those doghouse caps read as high as 456 volts when powering up then the highest one stabilized at 305 volts after about 10 seconds.

    Are F&T 22 microfarads 500V suitable replacements? or the 16 microfarads a better choice? The bulging doghouse caps are currently Mallory 20 microfarads 450V.

    I suppose since those are bad I might as well replace the cathode bypass caps too. I understand to keep the blue molded caps. Do you have a suggestion for the capacitor brand for those and the power supply filter cap?

    Also, Thanks for the shorting out the Vibrato pedal knowledge you are awesome! However, no luck on getting it to work. I traced the circuit around through the pots down to the optoisolator, to ensure wire continuity and swapped the tubes around. The optoisolator bulb read 7600 ohms. Is that normal? I will also order the .01 and .02 ceramic caps.

    Any tips about the optoisolator if I order the one for a tremolux from amprepairparts.com? That should be the correct type?

    Thanks again vinyl for the help, I really want someone to have a decent amp.

    I'm not sure you're understanding me. In this picture the clip lead appears to clipped to the "shield". The clip lead needs to be connected to the center pin on one end and chassis ground on the other.
    Quote Originally Posted by Garity View Post
    In this picture your'e measuring the resistance of the LDR, not the neon bulb.

    As to your other questions, F&T capacitors are a good choice for under the doghouse as long as they fit. For cathode bypass caps, you may be stuck with spragues.

    Don't forget the bias supply capacitor. When replacing make sure the positive side of the cap goes to ground, and the negative side connects to the negative side of the bias supply diode..

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Ok, the parts are on order and I will have them installed in about a week.

    Do you think it would be a good idea to remove the spare 6L6 socket and put an electrical box knockout plug there instead?

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Quote Originally Posted by Garity View Post
    Ok, the parts are on order and I will have them installed in about a week.

    Do you think it would be a good idea to remove the spare 6L6 socket and put an electrical box knockout plug there instead?
    if it's not too much trouble, save some poor SOB from losing their mind in the future "What DOES it DO?? Aarrrrghh"
    "Live and learn and flip the burns"

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Frankly, I'd be more inclined to part it out. Sell the blue molded caps, the late 63 output transformer, the early 64 choke, the "snowman knobs", and any pots that are original, the faceplate, and even the power transformer, even though it's not clear what that power transformer is. Yeah, it's a PITA to sell all of that stuff separately, but I think that's how you would get the most money out of it.

    The chassis is "toast".

    Hate to burst your bubble, but unless the price is unusually low, I don't think any one would buy this amp, except for parts to restore a different one. As a teaching tool, to learn something about old guitar tube amps it does have some value.

    Collectors will pay ridiculous amounts of money for a "clean' amp. Not sure if it's harder to find a collector, or a clean amp.

    JMO,
    vinyl

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Ok, Thanks vinyl. Unfortunately I did not see your part it out post until now, after I replaced the caps and got the tremolo working. (It was the "roach").

    Since this is a temporary educational amp now, while I was waiting for the parts, I drew the reverb circuitry and added it to a layout drawing.

    Could you explain to me what is going on with the additional tube circuitry? I understand how a triode works and if you inject a signal on the grid the resulting voltage across the plate resistor appears amplified and in the same shape as the grid voltage.

    One specific question I have is what is the purpose of the RCA jack connected to the transformer?


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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    Do all of the blackface fender amps that have reverb use a reverb pan? There is certainly no reverb pan with the amp. Could it be possible that RCA jack is for an external reverb pan?

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    Re: 1964 BF Tremolux With Mods - Anyone know what they are for?

    if the amp had reverb it had a pan, they didn't use external pans. Fender had reverb units since '61 but those went into the front of the amp.

    can you show the front and back plates of the chassis? I suspect that RCA you're seeing might be an add-on.
    "Live and learn and flip the burns"

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