Troubleshooting Tweed Tremolux Tremolo

[chopstuck]

I have a 5E9-A Tremolux and can'tget the trem working. Stared at it for hours hmmm- didn't work. Then checked V+ got a strage reading but can't figure out why. V3 has a 220K resistor from p1 to p6. I get a correct 355v on one side but insted of of 285v on the other side I get only 68v.
I have removed the 220k reisitor - value checks out. swapped out the .01 cap at the trem pedal as it had 30v on one side and 4v on the other. - nothing. All the original caps checked with less than 2mv leakage. It's pretty vintage so I don't want to replace everything willy-nilly.
I know it's a simple circuit and I should be able to figure it out. I tried once about 15 years ago but never could. The amp sound great- just no trem.

Any Suggestions ?

[Andy Le Blanc]

hey there....the oscilator is very gain dependant check the quality of the
bypass cap on the oscilator stage chathode.... should with a 3.3k resistor
also the caps in the phase shift line could be kaput
and if the amp is anything but untouched it might have been tinkerd with
so double check the hook up with a schematic just to be sure... it happens
and also check what style jack is used for the tremolo switch jack
there was some varience requireing or not requireing a foot switch.....
put a fresh tube it, one side is a follower thats power comes from the same
tap as the screen grids of the power tubes

[chopstuck]

Thanks, Andy .

I resoldered the connections and replaced the 12ax7. There was a 4750K between my plates and screens, replaced with a 2.2K. Voltages are closer. Now it beats but the outputs are gutless esp. as the trem depth is turned up. Amp wakes back up when I pull the tube out. Hmmm I'm drawing 23V across my 6V6 cathode resistor. But the amps sounds more thin / fizzy now. I may try upping the cathode resistor to get the umph back or shoud I try upping the screen resistor ?

Suggestions ?

[Firestorm]

Thanks, Andy .

I resoldered the connections and replaced the 12ax7. There was a 4750K between my plates and screens, replaced with a 2.2K. Voltages are closer. Now it beats but the outputs are gutless esp. as the trem depth is turned up. Amp wakes back up when I pull the tube out. Hmmm I'm drawing 23V across my 6V6 cathode resistor. But the amps sounds more thin / fizzy now. I may try upping the cathode resistor to get the umph back or shoud I try upping the screen resistor ?

Suggestions ?

With the tremolo engaged, most of these amps lose something. They only have two gain stages and one of those is the PI, so upping the PI cathode voltage as this kind of tremolo does, will kill a fair amount of gain. Check the resistor values and make sure you've got good cathode bypass caps throughout the amp. 23V across the cathode resistor isn't out of line. The stock value for the screen resistor was 2500, but 2K2 should work fine.

How does the amp sound when you turn off the trem switch (either on the depth control or the speed control depending on the model) instead of pulling the tube?

[Andy Le Blanc]

the trem in these things is coupled with a chathode follower connected to the
bias resistor and bypass cap of the phase inverter and what your describing
is what they do...... its a tightrope between the effect and performance
there are other ways to connect the trem if you what to
Im assuming the 4.7k came out of the power supply tween the B+ and screens
later amps supplied the screens thru 470 ohm resistor s ...one each....
that might be the better mod for you expectations but it wont change the way
the trem interacts with the rest of the amp... if your gonna alter the bias
put a 1 ohm temporarily between the bias resistor and ground so you can measure static tube draw in ma.
you should be able to trim the effect by tweaking resistances around the depth control

[chopstuck]

I replaced the Asterons .01 , .01 and .02 with all new .02 OD's and wow got more effect - full on and off now. The depth is the limiting factor. Tone just turns to celophane as you turn it up. Kind of fizzes in-between the throbs. Still sounds better with the trem tube pulled out of the circuit. And, yes, all the cathode bypass caps are new. I guess I would be happy if i could get it to sound as good with the trem tube in when the speed swith is off. I guess iwill pull all the resistors in the trem circuit to check for spec. I think there is still positive bias v+ leaking on the grids when the effect is off.

I remember these amps used to sound so killer..

[dansamp]

can't offer any help but I too am struggling with a Fender tremolo
except mine is a blackface >
I am having a pretty similar problem one plate has proper voltage reading and the other one is about 70-80 v. too low
it was working great then crapped out
if i strum the guitar hard you can hear it but only one pulse
the photo cell light is very dim and the 50k depth knob is scratchy getting up towards 8-10
by the way staring at mine didn't work either

Dan..........

[jjman]

For the Tremolux I would compare the PI's cathode voltage with and without the trem tube plugged in. It should go up with the trem tube in but maybe it's going up too much.

Maybe the 100k resistor on the pot or the pot itself is out of wack.

[Firestorm]

I replaced the Asterons .01 , .01 and .02 with all new .02 OD's and wow got more effect - full on and off now. The depth is the limiting factor. Tone just turns to celophane as you turn it up. Kind of fizzes in-between the throbs. Still sounds better with the trem tube pulled out of the circuit. And, yes, all the cathode bypass caps are new. I guess I would be happy if i could get it to sound as good with the trem tube in when the speed swith is off. I guess iwill pull all the resistors in the trem circuit to check for spec. I think there is still positive bias v+ leaking on the grids when the effect is off.

I remember these amps used to sound so killer..

This not Fender's best attempt at a tremolo circuit; I've fought with many of them. There's no such thing as an Astron cap that isn't leaking, so it's good to replace the .02, which has to block the DC, but you might try putting the .01 Astrons back in. They will be leaking a little too, but that sometimes tames the tremolo.

Do you have the footswitch? It shuts off the tremolo in a different way than the switch does. Try using the footswitch (or just short the jack) and see if that produces a better result.

[Firestorm]

DELETE -- double post

[Firestorm]

can't offer any help but I too am struggling with a Fender tremolo
except mine is a blackface >
I am having a pretty similar problem one plate has proper voltage reading and the other one is about 70-80 v. too low
it was working great then crapped out
if i strum the guitar hard you can hear it but only one pulse
the photo cell light is very dim and the 50k depth knob is scratchy getting up towards 8-10
by the way staring at mine didn't work either

Dan..........

You can't trust the voltages published on the schematics for tremolo circuits, so don't sweat that. When blackface tremolos don't work, it is always one (or three) of three things: low gain of the oscillator tube (replace the cathode bypass resistor or the tube); current leakage in the capacitors in the phase loop (replace the .02 and the .01s with new 1KV ceramics); the trem "bug" is kerflooey (get a new one). The light dependent resistors (LDRs) inside the bug are really just photocells and they do wear out. AES has some that seem to work fine; there are also some expensive boutique ones that are claimed to be better, but I haven't tried 'em.

[dansamp]

You can't trust the voltages published on the schematics for tremolo circuits, so don't sweat that. When blackface tremolos don't work, it is always one (or three) of three things: low gain of the oscillator tube (replace the cathode bypass resistor or the tube); current leakage in the capacitors in the phase loop (replace the .02 and the .01s with new 1KV ceramics); the trem "bug" is kerflooey (get a new one). The light dependent resistors (LDRs) inside the bug are really just photocells and they do wear out. AES has some that seem to work fine; there are also some expensive boutique ones that are claimed to be better, but I haven't tried 'em

Firestorm, thanks for your input
I have tried different tubes,
this circuit did not have a cathode cap across the 100k (later silverface)
I did add one, checked and have tried different feed back caps 02,01,01
I tore apart the photocell and found the bulb to be very weak that's when I discovered if I hit the strings hard the intesity of the light increases
I subbed in another bulb and taped it back together but no good
I do notice that the intesity pot is scratchy at its top most travel but I tried a different pot (not revers audio)
didn't change it
the bad thing is this was working great and I was done servicing the amp otherwise
I had put it back in the cabinet and was playing it for a while
then the next day it stopped working

Dan........

[chopstuck]

Firestorm and JJman -thanks for the input. I will try returning the .01 Asterons and thanks for the heads up on the PI cathode voltage. It really changes the amp with the trem tube in there. When I ground the pedal jack it just stops occilating and doesnt change the tone. I really like the Vibrolux / Gibson GA-18 circuit much better. I may just build one of those once I get this working well enough to pass judgement on it.

[Firestorm]

Firestorm, thanks for your input
I have tried different tubes,
this circuit did not have a cathode cap across the 100k (later silverface)
I did add one, checked and have tried different feed back caps 02,01,01
I tore apart the photocell and found the bulb to be very weak that's when I discovered if I hit the strings hard the intesity of the light increases
I subbed in another bulb and taped it back together but no good
I do notice that the intesity pot is scratchy at its top most travel but I tried a different pot (not revers audio)
didn't change it
the bad thing is this was working great and I was done servicing the amp otherwise
I had put it back in the cabinet and was playing it for a while
then the next day it stopped working

Dan........

I can't imagine why hitting the strings hard would have that effect on the neon bulb; if anything that should sag the power supply and dim the light. BTW, in my experience, it's more often the photocell rather than the neon lamp that goes south. Sometimes they seem to work a little and then just crap out.

The other thing to check in a blackface is to make sure the footswitch is working and the the plug and jack are making good contact. These amps use the negative voltage from the bias supply to shut off the oscillator, so when the footswitch is "on" it grounds out the negative voltage and let's the tremolo work. So if the footswitch connection is bad, it might not be grounding out the negative voltage.

[dansamp]

I can't imagine why hitting the strings hard would have that effect on the neon bulb; if anything that should sag the power supply and dim the light. BTW, in my experience, it's more often the photocell rather than the neon lamp that goes south. Sometimes they seem to work a little and then just crap out.

the neon bulb I am talking about is the one in the photocell
I took the cell apart because I couldn't see any light coming through it so I figured it was bad, when I opened it up I could see a very dim light, that's when I noticed it would get brighter if I hit the strings harder

before ordering a new one I figured I would replace the bulb since I found one in my stash of parts
it did not change anything.

thanks for your input

Dan....