65' Fender BF twin reverb-Tremolo / Vibrato non-functioning help!

[bbrownsbrick1]

im a novice, just some background info. i just got an original BF 65' twin reverb for an absolute steal (360 US), all is functioning EXCEPT for the vibrato (or tremolo is a more accurate description). before i attempt to recap/replace resistors, etc., i was wondering what the likelyhood that the optical LDR has gone bad, and how can i test it? its activated by the #ON# bulb. i was also wondering the best to go about this. details would help! thanks a lot!

[bnwitt]

Triple B, are you talking about a Reissue model? Have you tried swapping tubes in the amp?

[bbrownsbrick1]

nope, this is an ORIGINAL, dated I0, Sept. 65. Yes, i did try tube swapping. it appears that the previous owner had replaced all of the coupling caps as well. the opto isolator looks like a little roach of some sort, it DEFINITELY looks original. is there anything i should test along the way so i dont just shell out 16 dollars on this esoteric part of fender history?

[vinman753]

I'm taking a guess here, but I ran into this with another amp. The footswitch might have to be connected for the tremelo to work.

[52 Bill]

I'm taking a guess here, but I ran into this with another amp. The footswitch might have to be connected for the tremelo to work.

Vinman is right, this amp has to have the footswitch in it to work. Just short the rca jack on the back panel with a jumper.

If the oscillator is working you will see the flashing neon light inside the roach. If the oscillator will not run, check the three feedback caps and the cathode bypass cap in the phase shift circuit.

[bnwitt]

is there anything i should test along the way so i dont just shell out 16 dollars on this esoteric part of fender history?

Well you could check to see if the oscillator is oscillating before you replace the roach. This is best done with a scope but could be done somewhat with a multimeter. Test voltage to ground at the junction of the 10meg resistor and the leg of the roach to see if it is fluctuating. Do you have the footpedal? If not you can take a phono plug, stick it in the vibrato pedal jack and short it to turn on the vibrato. The light from the emiiter part of the roach can be seen through the ends of the rubber tubing when it is working.

[bbrownsbrick1]

yes, i dont have the footswitch! i will look into all of this! so 65 fender bf reverbs need the footswitch for the trem to work? is there any way to internally "fake" the footswitch. im not doubting any of this, just want some more re-inforcement. thanks so much

[bnwitt]

is there any way to internally "fake" the footswitch.

Read the posts carefully. you just need a shorted phono plug plugged into the vibrato pedal jack

[52 Bill]

As you research this question, you will learn that 99% of all Fender amps need a pedal for the vibrato function to work.

Originally if they didn't have a footswitch, they were supplied with a shorted RCA plug that could be placed into the footswitch jack on the back panel of the amp.

[bbrownsbrick1]

ok, i shorted an RCA jack and taped the ends toghether, plugged it in...the vibrato sounded great! thanks so much for the help. now i just have to deal with feedback from the reverb.

[psyops70]

You are right...I have a 20 year old 65 Twin Reverb and left my footswitch at my Colorado cabin and now I'm lost in Maine with no Vibrato..have to buy a new footswitch.

Thanks and here is a link:Fender Twin - Wikipedia, the free encyclopedia The front panel also has a bright red pilot light lens (better known as "pilot lamp jewel" for its multiple triangular-shaped facets), covering the pilot light (made by the Chicago Miniature Lamp Co.). Other colour schemes (amber, white, green, purple and blue) are also available.
Rear panel controls include a 2.5-amp "slo-blo" fuse, an accessory AC outlet, an earth ground selection switch, on/off and standby switches. Additionally there are two speaker output jacks, and jacks for footswitches to activate/deactivate the reverb and vibrato effects.
The black faceplates of the "blackface" era Twin Reverb will say either "Fender Electric Instruments" (FEI) or "Fender Musical Instruments", (FMI) depending on the date of manufacture. Those units made before the CBS take over of Fender in 1965, will be marked Fender Electric Instruments, and be worth a bit more on the collectors market.