Tremolo not working in Fender Princeton Reverb AA1164 replica

[SleepLess]

Hi!
I finished my PR replica yesterday. All is fine except that the tremolo effect is not working. Other than that really great sound and lush reverb. I have studied the layout all day and can't figure out what's wrong with what I did. I added a 10KL bias pot to the stock schematics and that's it...

The .02 ceramic cap eyelet that goes to V4 pin 1 shows 227V DC.
The middle lug of the intensity pot shows -35V DC.
I have a 393V B+ and the amp is biased at 24mA.
Just in case it might change things the amp is wired for 240V operation since I'm in the EU.

If you got any idea, I'm all ears...

Here are some pictures if they can help:









Thank you guys!

[phsyconoodler]

Try another tube first,then give us tube pin voltages.Then triple check your wiring.
   If you have a meter with a graph feature on it it will help figuring out if it's oscillating.The plate voltage will jump all over the place on the output tubes.And the tubes will visibly pulse as well.Try backing the bias off to about 18ma as well.
  If that helps there are some tricks to get it to be stronger,but check all the basics first.

[SleepLess]

Thanks a lot!
I rechecked my wiring and I actually had reversed the speed and intensity wires going to the .1uF SoZo cap and the .02 ceramic cap. I haven't checked the result yet, I have just finished resoldering but I think that was my mistake...

Thanks, that was my fault using only white wires... Should have labeled them...

[ThermionicEngine]

Nice clean build! 

[SleepLess]

Nice clean build! 

Thanks a lot! It's my first PR!!! I built about ten Marshalls and two Tweed 5E3 before though, I'm not a noob in amp builds...

[phsyconoodler]

Yes,nice build! Glad you may have found the issue.You should display your work in the 'media gallery' so the rest of us can see how sloppy our work is compared to yours!!

[Fresh_Start]

Looks really nice!  Please add gut shots to the Gallery as physco requested.

Using different colored wire for specific things helps keep me out of trouble... at least some of the time.  My scheme wouldn't have helped in this case though.

Cheers,

Chip

[SleepLess]

I will post pictures, but I can't seem to find the gallery anywhere...

Oh, and the tremolo is still not working btw... 

[Willabe]

You do very nice work!

Pics gallery, go to top of page look on the left, click on,--    Media.


       Brad         

[SleepLess]

Here are my readings, everything in DC except pins 4, 5 and 9 AC, everything was measured with the reverb jacks and the pedal disconnected.

V1:
1             173.4V
2             0V
3             1.34V
4/5         0.79V
6             174V
7             0V
8             1.3V
9             5.34V

V2:
1             384V
2             0V
3             7.45V
4/5         0.79V
6             379V
7             0V
8             7.45V
9             5.26V

V3:
1             169V
2             0V
3             1.34V
4/5         0.65V
6             164V
7             0V
8             1.39V
9             5.32V

V4:
1             176V > 280V
2             -1.3V > 1V
3             1.81V > 2.55V
4/5         0.6V
6             241V
7             25.4V
8             73.3V
9             5.1V

Please help me out, I’ve never had such a hard time with an amp build…
Thanks,

[phsyconoodler]

Looks like V4 is oscillating.Now pull the power tube bias back to about 16-18ma and see if you get any love.Turn the intensity all the way up.If you get something then you have a working trem that needs a bit of tweaking.If not there is still something mis-wired or a bad ground somewhere.

[SleepLess]

OK, it's biased in the 16/18mA range and now I'm getting something but it's faint. I really have to put the intensity on 10...

I maybe should have said that I have a 100uF/100V cap on the bias board instead of the 47uF/100V and that my resistance on the bis pot is a 22K instead of a 27K. If that helps...

Thanks already!

[phsyconoodler]

If you have a jumper wire,put a 2meg resistor from the trem footswitch jack pin to ground.Any more trem?

[SleepLess]

I'll solder a 2M resistor where you say tomorrow and see, I'm kinda disappointed that the tremolo will not work with the stock values though... That's a bummer. I hate tweaking, it always means that you're catching up on something that was wrong from the start...

Thanks a lot for your help phsyconoodler! I'll write tomorrow, it's midnight here and everybody's asleep, I can't wake up anyone with my tremolo now... :)

[phsyconoodler]

It may not be the answer,it just may point you in the right direction.If this increases the trem strength it means you have a bad resistor or cap that's causing an issue for you.Sometimes going over the entire tremolo circuit with an ohmeter and a soldering iron can help.Don't forget checking for grounds on the input and speaker output jacks.

[SleepLess]

So I do have some tremolo but I have to turn the intensity pot all the way up. I don't have any 2M resistor at hand. I tried with a 1M but it didn't seem to work.

Here are two more pics of the RCA jacks and the speaker jacks. Maybe you'll find something. The layout I had was kinda crappy, many info were missing. There may be a ground that I didn't solder or whatever... It's funny how this amp has turned me into a complete noob. I feel like I'm back to my first amp build... All shaky inside 'cuz I can't figure out waht to do and what's wrong...
Thanks!

[SleepLess]

Right,
So after some further playing and testing, I find that the tremolo is working OK. It's very subtle to say the least. Below 5 it's almost as if it wasn't there, and on 10 it's totally bearable. I used to have a Super Reverb that had a tremolo that sounded a lot clearer and powerful. Maybe it is due to the optocoupler vs the ceramic discs...
What would you guys say? Is the Princeton on the subtle side of the tremolo or should it be tremendous on 10? Since I don't have a 2M resistor I can't try what phsyconoodler advised but if you got other tips... The speed pot works really well, the whole amp sounds gorgeous, it's just that I think the tremolo is a little weak. Tell me what you think.
Oh and I checked all the values of the resistors on the board and they're all within specs. The ceramic discs are all right on the spot as well... My lead dress is now good as well.
What do I do? Stay with my 16mA bias? Reduce it even further to have more trem? Put it back up to 24mA? Let me know your thoughts!
Thanks!

[sluckey]

What do I do? Stay with my 16mA bias? Reduce it even further to have more trem? Put it back up to 24mA? Let me know your thoughts!

You may have to compromise.

But try this first. Reduce the size of the circled 1Meg resistor to increase the trem strength. Don't be afraid to take it down to 100K. Rather than totally removing the resistor I'd just tack solder a 220K across the 1Meg to be sure that the trem strength increases and sounds good.

[SleepLess]

Wow sluckey thanks a lot man, I swapped the 1M for a 220K and I now have a great great tremolo sound!!!! The amp is now officially complete and I can post a few pics in the gallery!!!

Just one more thing about bias: do you think I can bring it up to 23/24mA or do I leave it now at 17mA???

Thanks to all of you!

[LooseChange]

I've noticed that tremolo depth is related to the bias level. Too hot and you lose some depth.

[SleepLess]

OK? I'll keep it down at 17mA...

[sluckey]

I'd experiment.

[carausius]

Really nice work, put's me to shame 

BTW just wondering as your'e based in Europe which power transformer & rectifier tube type did you use for your build?

[SleepLess]

Transformers are from Mojotone/Heyboer. Tubes are all JJ's and the rectifier is a GZ34. I'll try NOS tubes and a 5Y3GT as well. It sounds awesome as it is already!