TS-808 doesn't scream : E only 0.45V lower than B it that reason?

[zjokka]

sorry guys I just hoped I could have done without another new TS debugging thread. but they all far from conclusive.

1.What does it do, not do, and sound like?
Sound comes through as if in bypass, none of the controls seem to work
2.Name of the circuit
Tube screemer 808
3.Source of the circuit (URL of schematic or project)
www.generalguitargadgets.com
4.Any modifications to the circuit? Y or N = YES
5.Any parts substitutions? If yes, list them.
Glass Germanium diode in D3
6.Positive ground to negative ground conversion? N
7.Turn your meter on, set it to the 10V or 20V scale. Remove the battery from the battery clip. Probe the battery terminals with the meter leads before putting it in the clip. What is the out of circuit battery voltage? => 9.03V
Now insert the battery into the clip. If your effect is wired so that a plug must be in the input or output jack to turn the battery power on, insert one end of a cord into that jack. Connect the negative/black meter lead to signal ground by clipping the negative/black lead to the outer sleeve of the input or output jack, whichever does not have a plug in it. With the negative lead on signal ground, measure the following:
Voltage at the circuit board end of the red battery lead =9.03V
Voltage at the circuit board end of the black battery lead =0.00V

Now, using the original schematic as a reference for which part is which (that is, which transistor is Q1, Q2, etc. and which IC is IC1, IC2, C1, and so on) measure and list the voltage on each pin of every transistor and IC. Just keep the black lead on ground, and touch the pointed end of the red probe to each one in turn. Report the voltages as follows:

Q1 C = 9.03V    B = 3.67V  E = 3.22V
Q2 C = 9.03V   B = 3.66V  E = 3.21V

IC1 (or U1)
P1 4.52     p6 4.44
P2 4.57     p7 4.43
P3 4.48     p8 9.03
P4 0
P5 4.44

D1
A (anode, the non-band end) = 4.5
K (cathode, the banded end) = 4.5

D2
A = 4.5
K = 4.5

D3
A = 4.5
K = 4.5
-----------------------

I checked all the connections on the pots, but connecting the the wrong way might not be the cause. The leads don't short and are connected to the pots, the pots work. Initially I used 1N4401 transistor with lower gain, but changing to 1N5088 didn't change anything.

I have to leads for the Clean Mod (cutting the diodes out) and checked: infinite resistance between the leads..
Only thing I can see is the voltage difference between B and E on the transistors isn't the mandatory 0,6 but close...

Did learn with search button that resoldering the whole board  sometimes works, a TS8 sometimes works without correct voltages on the transistors, that a 1N5088 sometimes helps (not in my case though) and that if everything is ok but the transistorposition wrong, there is hiss. Some old threads are similar of my problem but remain inconclusive.

thanks for having a look,
zj

[petemoore]

  I would audio probe it.
  The IC Voltages look pretty good/ The transistor voltages...not exactly sure, they are close to the same so probably they're ok, lemme see...Buffer voltages, I do believe the base needs to be at least one diode drop above the emitter .6v or so...the probe should be able to tell if there any difference in sound between the Q inputs and their outputs, there shouldn't be 'any {Very little].

[R.G.]

The voltages look OK-ish. Some high gain transistors pull so little base current that they can have a Vbe of 0.4-0.5V. I would look for something else first.

My first guess would be miswiring of the bypass switching.  Check that first, perhaps with an audio probe, and only dig into the circuit more if you actually have audio going to the circuit.

[zjokka]

  I would audio probe it.
  The IC Voltages look pretty good/ The transistor voltages...not exactly sure, they are close to the same so probably they're ok, lemme see...Buffer voltages, I do believe the base needs to be at least one diode drop above the emitter .6v or so...the probe should be able to tell if there any difference in sound between the Q inputs and their outputs, there shouldn't be 'any {Very little].

The voltages look OK-ish. Some high gain transistors pull so little base current that they can have a Vbe of 0.4-0.5V. I would look for something else first.

My first guess would be miswiring of the bypass switching.  Check that first, perhaps with an audio probe, and only dig into the circuit more if you actually have audio going to the circuit

Thanks, guys.

First and foremost:  RG, I didn't wire up a switch yet.

Did do my homework, but didn't use the probe yet, as I'm getting playtrhough all the time. Debugged some circuit with the probe when there was no sound coming through. Now sound is coming through but undistorted, so I guessed cutting OUT a part of the circuit would be very unlikely to bring the distortion the whole board should but cannot generate. Or where should I probe?

Thought about diodes, but as the voltages check out    Like I wrote did use a odd (will try to identify later) germanium glass diode.
Then there's the pot's that don't affect anything at all -- isn't

Do remember some real stompbox voodoo that happened when I first plugged it in - no  sound at all. Because I thought I might have switched in and output in the untagged wiring layout at ggg, I switched in and output, still nothing. Checked diagram, concluded it was correct the first time, switched back -- I get sound, clean as can be. I plugged the pots into breadboard so I can easily connect and discoonect the pots. Although they all show correct continuity, they don't crackle even when I pull them out.

i'm sure I'm missing something here...

zj

[zjokka]

could somebody hint me at the voltages for the pots?
audio probing isn't giving any results other that what I already had.

don't understand how to troubleshoot the pots. did check the values and whether they worked and the connections, but...nothing.
how exactly do the pots interact with the board?

Vr= 4.5V right? that's what I'm reading on the pots.

sorry for these perhaps silly questions
j

[petemoore]

could somebody hint me at the voltages for the pots?
  Nope, the pots vary resistance, turn the pot [connected using 3 lugs] and the wiper to lug 1 resistance goes down, the wiper to lug 3 goes up...vice versa when turning it the other way, all the way either way and the wiper is Connected to an outside lug.
  Use DMM to test the resistances of pots, rotate very slow and look for 'dead spots' you should have fairly smooth rise/fall of resistance when adjusting the pot...analog tapers will taper...big resistance change toward one end of shaft rotation, small resistance change at the other.
audio probing isn't giving any results other that what I already had.
  Not clear...you are losing signal right at the input?
  Connect probe to guitar cable [ground], you should hear guitar
[don't forget the groundS, check 'em all with a DMM lead clipped to a ground, other lead should cause a DMM beep at all other ground points].
  Ok, so the probe is seeing guitar signal at input, you hear guitar, now try it at the next point of the signal path in the circtuit [that's a capacitor, input cap], next on the other side of the 1k...listening for what the signal is doing as you work your way from signal input toward middle, signal output.
  try the opamp inputs and outputs. 1,2,3 [for oa 1], and 5,6,7 [for OA 2]
  You're looking for signal loss anywhere, I believe the first opamp provides the most gain...confused here myself...there should be at least unity, and a good bit of gain happening with the chip, first stage for sure if the gain is turned up.
  Anyway, probing the signal path of the circuit may reveal the approximate location of the problem.