Anemic sounding Boss TR-2 Tremolo

[BDuguay]

I found those specs too, thanks. It's this bloody D11 that has me perplexed! I tried a 8.2v zener and I got a super distorted signal. I'm wondering now if I can just put a 1N4004 there and hope for the best. This is near impossible to solve without the right schematic.

[ElectricDruid]

Hang on, can we back up a bit please? I'm lost.

You *were* having problems with the tremolo sounding anemic, and now you've dug up a thread from 2017 where you were having problems with a similar unit, and you're chasing off over some diode or other? Why? What's that got to do with anything? What makes you think it's important? You said the op-amp voltages weren't right, but you didn't post them, so we don't know and can't help you by checking.

Give us some more information and we can help. Otherwise you're just thinking out loud on the forum and we're sat here watching you. Ta!

[BDuguay]

My apologies, I've made this more complicated than it should be. I forgot that I had asked for help on this, the same pedal, back in 2017. The same problem still remains and that is what to put in place of D11.
Now I know this means nothing because there is no available schematic to reference for this particular version but, according to the information given to me from Roland, D11 is an 8.2v zener diode.
I bought some and have tried them but it gave a very distorted signal. Maybe I have the wrong zeners or something.
When the pedal was working for me, albeit with a volume drop, the zener I had installed was a 1N52 (the next two numbers are barely legible but I think it's 32) so that doesn't help. What I do know is it measured 6v dc in the circuit and I was only getting 2.5 v at pin 7 of the pampas. I just blindly figured that was too little voltage and that might explain the volume drop and general poor performance of the pedal.
I hope this clears things up.... a little.

[antonis]

Without knowing the role or circuit exact placing of than notorius D11, we can't tell much, can we..??

[BDuguay]

I will have a look at it again and attempt to explain its function in the circuit. I really wish there was a schematic out there!

[BDuguay]

Right after the power input, 1n4004 diode, and a 1k resistor is D11. (According to the message I got from Roland back in 2017, D11 is an HZS9A2. A search revealed it's a zener but was unclear what the voltage is)
After the 1k resistor is a 10uf cap and then on to a C2458 transistor. From there it feeds pin 8 of 5
NJM14558L opamps. This is not much to go on, I know. Hopefully it helps decipher this thing.

[antonis]

Right after the power input, 1n4004 diode, and a 1k resistor is D11. (According to the message I got from Roland back in 2017, D11 is an HZS9A2. A search revealed it's a zener but was unclear what the voltage is)
After the 1k resistor is a 10uf cap and then on to a C2458 transistor.

So we're talking about a n-p-n BJT used for voltage stabilization..
Considering D11 Anode is connected to BJT's Base, its value (voltage rating) should be about 0.6 - 0.7 V higher than BJT's Emitter one..
e.g. for +5.5V, it should be a 6V2 Zener..  

But, without a precise schematic, we're just guessing,,

[BDuguay]

This is great news!
I'm going to put in a 6.2v zener and hear what happens.

[BDuguay]

My local store did not have the zener I'm looking for so it's off to digikey I guess. In the meantime, what are the chances that the original damaged D11 diode, with A62 marked on, was in fact a 6.2 volt zener. The marking on it is very convincing. Just a thought.

[antonis]

For testing purpose(*), you can use almost any zener availiable by adding or subtracting effective voltage with the use of silicon diodes..

(*) Temperature stability/drift shouldn't be your main concern..

[BDuguay]

I think I follow. How could I reduce an 8.2v to 6.2v as per your suggestion?
Thanks!

[antonis]

Either by adding 3 X Si diodes (better power diodes , like 1N400X, due to their forward voltage drop approx. 0.7V) between Zener's Cathode and BJT's Base or by implementing a 18k/56k voltage divider..
(18k to Zener Cathode, 56k to GND and their junction to BJT's Base..)

[BDuguay]

I got a hold of some 6.2 v zeners but the result is still the same, a weak and poor sound. I went back through all these posts and all my research and everything points towards the need of a 8.2 v zener.
I have some of those, 1N5237B, and have tried them but the result is I have to hammer the strings to get any signal, bypassed or engaged, and the sound is best described as 'splatty' and barely there.
My question is am I missing something regarding the specs of the zener? Is it possible there's a rating that's not up to the task?
Again, thanks in advance.

[Mr.Kite]

still the same, a weak and poor sound.

I'm not sure to get what you mean.

"Weak and poor" like the input jack barely makes a connection or like "the sound is there, but is it supposed to sound like this"?

Are you 100% sure there's something wrong with the pedal or there's a small chance that you simply "hate" the sound\design of this pedal?

I ask because it's pretty common for Tremolo pedals without some sort of boost\volume control (TC Electronic Vintage Tremolo has a volume control for example) to sound weak, with a noticeble volume drop.

Think about it, this kind of tremolo effect is at the input of the amp and it works by chopping off a good part of your signal (that's what you do to get tremolo, amplitude modulation).

So, if the amp is set really clean, at low volume, without any breakup\compression, the pedal can easily sound weak and anemic, half volume of your dry signal.

If you push the amp more or use some sort of drive\compression after the tremolo pedal it shouldn't be a problem: maybe the tone will still get cleaner with the tremolo on, but you shouldn't perceive a volume drop or a radical change in tone.

It's just an hypothesis.

I say this because when I bought my first used Boss RV-2 I found it noisy: not too much actually, but the background noise was really weird\random. So I thought that there could have been a problem with that unit. I wasn't 100% sure if there was something wrong, but didn't sound normal neither. So I bought a second one and came to the conclusion that they all exibit this weird\random background noise. It's not that prominent and they sound great actually, but I'm happier now that I know that my unit is not faulty.

If you're not 100% sure that your unit is unmistakably broken I warmly suggest you to:

1) Try different settings on the amp, introducing more and more breakup\compression and see if the problem persists.

2) Buy a second one (you can find them for pretty cheap on the used market) and compare the two units, maybe they just sound like that and it's not a pedal that works well with your setup.

Otherwise, please provide as much information as you can (maybe make a short video\recording of the problem too) so that people more knowledgeable than me can help.

Just my .02!

P.s.
A little research and I found that the TR-2 was known for a pretty huge volume drop, until a later version came out, and the trimpot should be an internal volume\boost control! Maybe it's set too low for the way you're using it, but IMHO you should try what I suggested you above first.

[BDuguay]

Thanks for replying to my post. I'm convinced that this tremolo is voltage starved using the 6.2 zener diode. As I mentioned in a previous post, I had a working TR-2 that I took measurements from and that one measured 8.2 volts at its zener. There's one more thing I'm going to try later and hear if the performance improves. I hear your suggestion but I have no way of posting a demonstration video. My 32gig iPhone is almost completely full so there's not enough room for it. Like I said, the pedal works but it's definitely not currently working to its maximum potential.
B.

[BDuguay]

I was looking at it again and discovered that power comes in and feeds the collector of a C2458 transistor. The base of the transistor is fed the incoming power through a 1k resistor and the mystery zener diode to ground. That is where I measured 8.2 volts.

[antonis]

I was looking at it again and discovered that power comes in and feeds the collector of a C2458 transistor. The base of the transistor is fed the incoming power through a 1k resistor and the mystery zener diode to ground. That is where I measured 8.2 volts.

If that "that" is BJT's Base then you should measure about 7.5V on its Emitter..

Assuming 9V power supply and neglecting Base current, Zener current is about 800μA [(9-8.2)/1000]
(actually, a bit smaller due to "some" current going into Base..)
Dunno if this current is enough to bring Zener to its nominal knee voltage..

I'd try a smaller value resistor (put another 1k in parallel) to see what is going on..      

[BDuguay]

Yes."That" is the C2458 transistor.