Hoffman Princeton Reverb Trem-O-Nator Upgrade

[purpletele]

Steve,

I'll be happy to use my Princeton to see if the TON Mod works there as well.  I started looking at the schematic and layout and I have a high comfort level.  However, I don't like to bet on my electronic assumptions.  It would be a wonderful addition to the Princeton file if you could do some Visio work on the layout for documented reference.

I should have all of the parts ready to go and plenty of time.  Filing for a small business bailout tomorrow.

Thanks

BV

[sluckey]

Post a hi-rez gut shot pic of your PR.

[sluckey]

I think this will work. Any questions?

[purpletele]

Here are some photos of the Princeton Reverb

[purpletele]

I think this will work. Any questions?

That is fantastic!  No questions

Thank you

BTW, replaced the 100KL with 100KA on the Deluxe and it worked well.

[sluckey]

Have you started this project? Please take my Trem-O-Nator poll...

     http://el34world.com/Forum/index.php?topic=25762.msg279761#msg279761

[purpletele]

Have you started this project? Please take my Trem-O-Nator poll...

     http://el34world.com/Forum/index.php?topic=25762.msg279761#msg279761

I just received the caps that I needed.  I should be done in an within an hour.  I thought I took the poll, I don't want to flatten the curve.  Can you tell who submitted?

[sluckey]

I'll be around all day. Hopefully this will go smoothly. 

The poll is totally anonymous and you can only vote once so you won't flatten the curve. And you can vote without leaving any comments. I'm just trying to gather some stats with the poll but I'm really more interested in who has tried this and their opinions. I know there are several other members that have done this but the original "more tremolo" thread is just too long and bogged down with other details. I thought this thread would be a good way to collect opinions and such.

This is all for my curiosity. Ain't gonna be any TON kits offered from me. Can't say that someone else may try to make a buck from this idea, but just remember, all my stuff is offered freely. To quote Cheech or Chong, "I plead insanity your honor. I'm just crazy about this shit!"

[purpletele]

I'll be around all day. Hopefully this will go smoothly. 

The poll is totally anonymous and you can only vote once so you won't flatten the curve. And you can vote without leaving any comments. I'm just trying to gather some stats with the poll but I'm really more interested in who has tried this and their opinions. I know there are several other members that have done this but the original "more tremolo" thread is just too long and bogged down with other details. I thought this thread would be a good way to collect opinions and such.

This is all for my curiosity. Ain't gonna be any TON kits offered from me. Can't say that someone else may try to make a buck from this idea, but just remember, all my stuff is offered freely. To quote Cheech or Chong, "I plead insanity your honor. I'm just crazy about this shit!"

The mod went really smooth, the amp plays nice but no thump. 

I am getting 1.5 volts to the positive leg of the LED.  Everything seems to be wired correctly, I am going to try my last LED to see if it is bad part.

Update: The new component didn't work.  I'll try connecting the right lug of the intensity pot to V3-7
Update #2: Connecting the right lug of the intensity pot to V3-7 did not work

[sluckey]

Hold off a bit. Those Vactrols are sensitive. Divide and conquer! First let's make sure the oscillator is working.

Pull the Vactrol out. Put a red LED in it's place. LED anode connects where the Vactrol positive lead was connected. LED cathode (flat side) connects to ground. When you have a blinking LED then replace with the Vactrol.

[purpletele]

Hold off a bit. Those Vactrols are sensitive. Divide and conquer! First let's make sure the oscillator is working.

Pull the Vactrol out. Put a red LED in it's place. LED anode connects where the Vactrol positive lead was connected. LED cathode (flat side) connects to ground. When you have a blinking LED then replace with the Vactrol.

OK I have a red light but it is not pulsting

[sluckey]

Is the LED installed correctly? What is the voltage at Node B? What are the voltages on pins 1, 2, and 3?

[purpletele]

Is the LED installed correctly? What is the voltage at Node B? What are the voltages on pins 1, 2, and 3?

I have the doublechecked the LED
Node B is 383 V

V4-1  +- 100 V (varying)
V4-2  +- 200 mV (Varying)
V4-3  1.6 V  The red light pulsates when I measure voltage

[sluckey]

That's all good. This circuit is exactly the same as the last one you did, at least it's supposed to be. Let me compare you pics to the layout and see if I can spot something. Meanwhile, you compare the layout with your actual amp. Hopefully one of us will spot something.

[purpletele]

That's all good. This circuit is exactly the same as the last one you did, at least it's supposed to be. Let me compare you pics to the layout and see if I can spot something. Meanwhile, you compare the layout with your actual amp. Hopefully one of us will spot something.

I'll do that.  The amp sounds nice so I don't have collateral damage hanging over my shoulder.

Also, the 100Ka Reverb Pot works very well on the AB763 as well as this PR

[sluckey]

I don't see any boogers. Do you have some more red LEDs? If so, put a fresh one on the board. Reflow all the solder joints associated with the oscillator.

[purpletele]

I don't see any boogers. Do you have some more red LEDs? If so, put a fresh one on the board. Reflow all the solder joints associated with the oscillator.

I'll search, the one I have is from a pedal kit.  I'll reflow things and see. 

Why would I get pulsation in the LED when I am probing in that circuit?

[sluckey]

That is the puzzle. Ain't right. We want the LED to pulse all the time.

[sluckey]

Measure resistance from V4 pins 2 and 3 to chassis.

[purpletele]

Measure resistance from V4 pins 2 and 3 to chassis.

V4-2  1 meg
V4-3 10K

[PRR]

> V4-3  1.6 V  The red light pulsates when I measure voltage

When you measure voltage at cathode??

Put a 10k (5k-500k) across the LED. Maybe the LED leakage is SO low that the tube goes OFF and never comes back. The meter-load keeps it alive. (I don't like this story but you guys are straw-grasping.)

Else you have to leave the meter in the amp.....

[sluckey]

> Put a 10k (5k-500k) across the LED.

There is a 10K across the LED.

[sluckey]

Some things to try. Report findings.

[Willabe]

Else you have to leave the meter in the amp.....

       

[purpletele]

Update on the TON Mod

I got as far as replacing the .022 with the original .01.  That yielded pulsation in the little LED.

Should I continue with changing the 470K resistor back to the 220K?  Or do I drop the Vactec LED back in to check for intensity?

[sluckey]

Does the speed control change the speed of the LED flashes?

I really don't suspect that .022 cap. I rather suspect the solder joint. But, new caps have been bad before. When you get the TON up and running, then decide if the speed range is slow enough for you. If not, put a fresh .022 cap back in.

Leave the 470K on the board. We really want this TON to be exactly like your other TON.

The LED made it easy to troubleshoot the oscillator but now it's time to put the Vactrol back in. Remember, you may need to experiment with the value of the INT pot. Let your ears make that determination.

I'm cutting grass but will check back in about an hour. Got my fingers crossed for you.

[purpletele]

Update:

I left the .01 cap in there for now.  The intensity is barley detectable.

[sluckey]

Time to experiment.

[purpletele]

Time to experiment.

I ordered a 250 ka and a 500 ka Pot for the exercise



 

[sluckey]

There should have been a 250K pot in the amp before you started this mod.

[purpletele]

There should have been a 250K pot in the amp before you started this mod.

Correction

I ordered Reverse Audio pots to be consistent.

That will be a few days, should I move forward with anything else?  220K resistor and play with 10K cap?

[sluckey]

Take the 50K pot out and put the 250K pot in. Don't have to be reverse audio to test.

Forget about the 10K and 220K. The oscillator is working fine.

The only experimenting you need to do is with the value of the INT pot and where to connect it to the circuit. I showed you an alternate place to connect the INT pot. You're pioneering in unknown territory. I'm learning as we go.

[purpletele]

Take the 50K pot out and put the 250K pot in. Don't have to be reverse audio to test.

Forget about the 10K and 220K. The oscillator is working fine.

The only experimenting you need to do is with the value of the INT pot and where to connect it to the circuit. I showed you an alternate place to connect the INT pot. You're pioneering in unknown territory. I'm learning as we go.

Got it

I'll try a few things tomorrow

Thank you

[purpletele]

I changed the Intensity Pot to 250Kl.  The results were that the Tremolo was more detectable but it had to be dimed, also the speed needs to be at 6-7 for the Tremolo swirl to sound decent.

I switched the Intensity insertion point to V3-7 and that eliminated any modulation. kept the modulation the same as the other point of insertion.

[sluckey]

A couple things to try...

Disconnect the ground wire from the INT pot. What happens?

Now do the two tests in the attached pic. What happens?

[purpletele]

A couple things to try...

Disconnect the ground wire from the INT pot. What happens?  When I disconnect the ground wire for the Intensity Pot I do not detect any change.  The Intensity needs to be up to at least 3/4 the way cranked and the speed needs to be at the same level or higher.

Now do the two tests in the attached pic. What happens?

Re-Stated Results
]Test 1: Both INT control wires disconnected, I jumped the connection as shown in Example 1. The modulation is only detectable when the speed is at 9 or 10


Test 2: This test resulted very much the same as above, except the Speed control would go down to 3 and then cut off. The volume was reduced when connected as such

[sluckey]

Both INT control wires disconnected, I jumped the connection as shown in Example 1. The results are that the Intensity control was now responding and being detectable from the off position up to 10.

Really! How do you explain that when the INT pot is totally disconnected? I'm beginning to think this amp is cursed with the same gremlins as your AB763.

BTW the speed and intensity pots should not interact with each other in a properly functioning circuit.

[purpletele]

Both INT control wires disconnected, I jumped the connection as shown in Example 1. The results are that the Intensity control was now responding and being detectable from the off position up to 10.

Really! How do you explain that when the INT pot is totally disconnected? I'm beginning to think this amp is cursed with the same gremlins as your AB763.

BTW the speed and intensity pots should not interact with each other in a properly functioning circuit.

You are right, what I reported didn't make sense, I have to repeat the tests. 

[purpletele]

.

  I'm beginning to think this amp is cursed with the same gremlins as your AB763.

The gremlin is most likely ME

I reposted results above

[shooter]

The gremlin is most likely ME

now I'm infected with results that don't make sense to me 
I love playing with bugs though 

[sluckey]

The gremlin is most likely ME

YES! It's that crappy soldering that you do. Clean it up!

[purpletele]

The gremlin is most likely ME

YES! It's that crappy soldering that you do. Clean it up!

Well I haven't killed the amp, it plays and sounds nice.  I have been enjoying it all afternoon.

I agree that my soldering could be better,  I look at the turret jumpers and the solder joints on this amp and I don't like them, the amp doesn't look that good.  It was built when I was being sued by an ex.  My re-soldering seems to be difficult lately as well.

I'll rework all of the jumpers and joints in that circuit and see if I can eliminate that possibility.

Thanks,

BV

[sluckey]

My crappy soldering statement was not meant to be hurtful. Rather I wanted to point out that your skills need a lot of improvement. Reliable, clean soldering is very important. Please take my criticism in a positive way.

I suspect that poor solder connections may be a factor in your wonky symptoms. But even more, that rosin crud on the board is most likely conductive and allowing leakage resistance between turrets. I suggest you revisit every turret with a CLEAN soldering tip. Heat the turret enough for the existing solder to liquify and add a bit of fresh solder. Then clean the board. Mineral spirits will remove that rosin flux crud. Apply with a variety of small brushes,,, paint brush, acid brush, toothbrush, Q-tips, whatever you have. Please, no wire brushes. I use a variety of brushes to clean my boards. I follow up the mineral spirits wash with denatured alcohol, using the same technique. Here's an example of what you should be striving to achieve...

     http://sluckeyamps.com/phoenix/p11_big.jpg

The end result looks good but even more important, the solder joints are solid and there is no chance of conductivity between turrets. And that means reliable. Gremlins have no place to hide.

Give it a try. I know you have time. You won't be disappointed.

PS... Denatured alcohol may be hard to find due to CV19. Isopropyl works good too, but I prefer the sweet smell of denatured alcohol. I've been using this cleaning technique for new builds and pcb repairs for about 45 years. It's worth the effort.

[purpletele]

My crappy soldering statement was not meant to be hurtful. Rather I wanted to point out that your skills need a lot of improvement. Reliable, clean soldering is very important. Please take my criticism in a positive way.

I suspect that poor solder connections may be a factor in your wonky symptoms. But even more, that rosin crud on the board is most likely conductive and allowing leakage resistance between turrets. I suggest you revisit every turret with a CLEAN soldering tip. Heat the turret enough for the existing solder to liquify and add a bit of fresh solder. Then clean the board. Mineral spirits will remove that rosin flux crud. Apply with a variety of small brushes,,, paint brush, acid brush, toothbrush, Q-tips, whatever you have. Please, no wire brushes. I use a variety of brushes to clean my boards. I follow up the mineral spirits wash with denatured alcohol, using the same technique. Here's an example of what you should be striving to achieve...

     http://sluckeyamps.com/phoenix/p11_big.jpg

The end result looks good but even more important, the solder joints are solid and there is no chance of conductivity between turrets. And that means reliable. Gremlins have no place to hide.

Give it a try. I know you have time. You won't be disappointed.

PS... Denatured alcohol may be hard to find due to CV19. Isopropyl works good too, but I prefer the sweet smell of denatured alcohol. I've been using this cleaning technique for new builds and pcb repairs for about 45 years. It's worth the effort.

Thanks, you have been correct many times before.  I'll work on cleaning it up.

[purpletele]

This board was really grungy, I felt like I was cleaning Tiger King's teeth.

Spent a lot of time refloating things and checking to see that I wasn't creating collateral damage.  The amp plays well and feels strong.  I modified the reverb with a 100 Ka Pot and it is much more forgiving and more quiet with a shielded cable.

With everything connected to the original TON configuration except the ground for the 250 kl Intensity Pot;

The intensity has to be at 9-10 and the speed at 9-10 for the modulation to be audible.  If I cut the speed below 9 then the modulation becomes undetectable.  When I dime the intensity the volume of the amp dips. 

I'll keep going if you have ideas. 

[sluckey]

Disconnect the ground wire from the INT pot. Any better?

Which meter do you have?

[purpletele]

Disconnect the ground wire from the INT pot. Any better?

Which meter do you have?

The ground wire for the Int Pot was left disconnected when I put it back to TON configuration.  The results from above reflect the Int Pot being disconnected.

The meter that I have is a Klein MM1000

When I reconnect the ground to the Int Pot there does not seem to be any change.

[PRR]

The meter that I have is a Klein MM1000

Nominal 10Meg on DCV; however my similar model seemed to be 6meg.

[sluckey]

I was hoping for a meter that was capable of reading the frequency and RMS voltage of the 5Hz sine wave on the plate of the oscillator. I can't say that the Klein will do that. Worth a try though.

So, purpletele, see if your meter will measure that low frequency ***AC*** voltage on the oscillator plate. If it can, report the frequency and the RMS voltage.
 

[purpletele]

I was hoping for a meter that was capable of reading the frequency and RMS voltage of the 5Hz sine wave on the plate of the oscillator. I can't say that the Klein will do that. Worth a try though.

So, purpletele, see if your meter will measure that low frequency ***AC*** voltage on the oscillator plate. If it can, report the frequency and the RMS voltage.

I am not picking up any frequency at V4-1     0.0 Hz
The AC RMS voltage is 24 V at V4-1