Fixed: Blew up my TS-9 Tube Screamer. Where do I start to look?

[Floyd Pepper]

A while back, someone gave me a broken original TS-9 Tube Screamer.  The diode to protect a reversed battery had blown.  I replaced it and all was fine until...

I chained several pedal off a single 9v supply.  As I plugged one of the jacks into the TS-9 there was a spark and the TS-9 was dead.  Well almost.  The guitar comes through OK when the effect's turned off but when you turn it on the LED lights up but no sound.

Before I start audio probing and de-soldering does any one have an clues where to start looking?  None of the components look like they've blown.

Thanks

[jrc4558]

Check if all the trransistors and the IC are receiveing proper V+.

[The Tone God]

Read the "What to do when it doesn't work" sticky and report back.

Andrew

[Floyd Pepper]

Thanks for the advice.  I've re-read the trouble shooting guides and searched for forum for expected voltages in the TS-9 but haven't been able to track down what's up.     Forgive me being clueless.  I've built pedals before and have just completed a (bypass) TS-9 clone but I've having trouble finding what's up with this original.

Here's the voltages I'm seeing:
Battery = 8.8
VR = 4.37

IC
P1 = 4.36
P2 = 4.37
P3 = 4.35
P4 = 0
P5 = 4.36
P6 = 4.36
P7 = 4.36
P8 = 8.77

I expect the input buffer transistor is OK as the pedal works when in bypass mode.
The Input buffer reads (transistor right near top)
E = 3.83
C = 8.8
B = 3.4

I'm not sure how best to label the other transistors but looking at the soldered side of the board they measure
(Top left is where it says Maxon on the board)
Far left (near top)
E = 3.77
C = 8.76
B = 3.34

At the top
Left
E = 4.32
C = 0.02
B = 4.07

Right
E = 4.32
C = 0.63
B = 4.33

In the middle left to right
E = 0.69
C = 0.71
B = 1.29

E = 0.26
C = 6.44
B = 0.69

E = 0.68
C = 0.78
B = 1.29

These collector values look very low to me.  My bypass TS-9 clone has over 8v at the collectors.

Are these values too low?

[petemoore]

  If you don't mind me using your example as a test for my debugging techniques...@@ Rate here goes..
  IC
P1 = 4.36 
P2 = 4.37
P3 = 4.35
P4 = 0
P5 = 4.36
P6 = 4.36
P7 = 4.36
P8 = 8.77
  The inputs and outputs are sitting near 1/2 v, right near middle between Gnd [pin 4] and V+ [pin 8], so looks like N/P here, if you think looks can be decieving then use an audio probe, but the chips pins look to be well within operational parameters.
   I expect the input buffer transistor is OK as the pedal works when in bypass mode.
The Input buffer reads (transistor right near top)
E = 3.83
C = 8.8
B = 3.4
I'm not sure how best to label the other transistors but looking at the soldered side of the board they measure
(Top left is where it says Maxon on the board)
Far left (near top)
E = 3.77
C = 8.76
B = 3.34
At the top
Left
E = 4.32
C = 0.02 [if this reading is correct the transistor will pass no signal]
B = 4.07

Right
E = 4.32
C = 0.63 [again if this transistor is a buffer the collector should be near or at V+]
B = 4.33

In the middle left to right
E = 0.69
C = 0.71 [here too the collector and other pins sit with little room for the signal to
B = 1.29 [swing

E = 0.26
C = 6.44   [not real sure
B = 0.69

E = 0.68
C = 0.78  [collector is lower than base is problem
B = 1.29
  I would look for something that could make all the transistors I Was able to comment on to be in a non biased state, something they all have in common like...uh...collector or emitter component or connections...see if someone who'se bell Does get rung on the ones I put not sure by responds. 
  Putting a link to the schematic would also be helpful, and looking at the schematic should give you ideas about ways to apply the DMM to test how close the circuit boards 'electronics' actually match the schematic...
  But I wouldn't react [ by altering the circuit] to a reading of lower value resistance than is marked on a resistor or schematic when using a DMM to measure a resistor *In circuit, perhaps there is an alternate current path causeing an 'anomalous reading.

[GBlekas]

I have not looked inside a TS in awhile but thought there were 4 transistors in the pedal.
I am not sure that I am reading what you posted correctly but are you saying there are 7 transistors in your pedal?

There is one input and one output transistor in that pedal. The collectors of both should be at or near 9 volts.

There are another pair of transistors that are used in the multivibrator circuit which turns the pedal on and off. It appears, from what you said, that the switching is fine so testing these two could be skipped. The off transistor voltage readings are probably a trannie in the off state.

since your op-amp bias appears correct then we can assume the caps in the power section are fine as are the caps in the voltage divider circuit.

Ah ha!  I got it!
You have a blown Jrc-4558
Static sensitive little bugger that one is.

Replace it and let us know if I was right.

Regards,
George

www.PedalworX.com

[petemoore]

You have a blown Jrc-4558
  I didn't see any signs that the 4558 would be called into questionability, I thought the bias voltages looked pretty good.

[burnt fingers]

I have a similar problem.  I have had a TS9 that my brother gave me.  He got it in 83'.  It hasn't worked in a long time and the symptoms are very similar to yours.  I havn't had a lot of time to trouble shoot mine. I'll let you know if I get a chance to crack it open.

Scott

[Floyd Pepper]

This schematic shows 7 transistors like I've got in my TS-9.

http://www.generalguitargadgets.com/diagrams/ts-808.jpg

[Floyd Pepper]

After continued voltage probing I'm getting somewhere....

The IC voltages don't change when I switch the pedal on or off.  (I expect this is normal looking at the schematic)
The C voltages to the 2C1815's in the audio circuit seem OK.
The issue seems to be with the flip flop circuit
The G on the 2SK30A's is < 1v.  Is this expected?
The LED turns on and off fine
Is it safe to jumper a wire from SW to SW in the schematic to bypas the flip flop?

Any further pointers greatly appreciated.  I think I've learnt more trying to debug this thing than I have done building and studying schematics.

Thanks

[GBlekas]

My experience tells me the bias does not change when an ic is hit with static discharge. Static is like 60000 volts but very low amperage but ic's are very sensitive to this.

What happens, in essence, is the op-amp developes an open in it's circuit. An open won't pass signal. Sometimes it is heard as a noise in with the signal, if not completely open and resembles out of spec transistors.

I say take the chip out and install a socket. Then try a new chip and then the original.

If it is in the flip flop circuit it would be a FET, most likely labeled 2sk30a on your schematic. This, I would think, is less likely but always possible.

Regards,
George

www.PedalworX.com

[GBlekas]

My experience tells me the bias does not change when an ic is hit with static discharge. Static is like 60000 volts but very low amperage but ic's are very sensitive to this.

What happens, in essence, is the op-amp developes an open in it's circuit. An open won't pass signal. Sometimes it is heard as a noise in with the signal, if not completely open and resembles out of spec transistors.

I say take the chip out and install a socket. Then try a new chip and then the original.

If it is in the flip flop circuit it would be a FET, most likely labeled 2sk30a on your schematic. This, I would think, is less likely but always possible.

Regards,
George

www.PedalworX.com

[Floyd Pepper]

Thanks GBlekas!

I socketed the op-amp, plugged in a new 4558 and I'm rocking again.   

Guess it makes sence - all the right voltages reaching the op-amp but no sound.  Wonder how I got the low voltage readings from the FETs.  I double checked them and they're as I reported.  Weird.

Just so you know, I blew the TS-9 daisy chaining a negative and a positive ground pedal off the same 9v transformer.  I blew the transformer and the tube screamer.  The Fuzz Face survived.  God know what I was thinking when I connected them all up.

[GBlekas]

You are welcome brother!

On a side note I have only ran accross this problem with the JRC4558 op-amp for some reason.


Regards,
George

www.PedalworX.com

[burnt fingers]

Well I guess I will take your lead and unsolder my chip, (if my voltages read correctly otherwise) I pulled a few JRC4558's from an old beat yamaha keyboard a while back.  I will keep y'all posted.

Scott

[MartyMart]

I had the exact same problem with a friends old '808 a few months ago.
Similar looking voltages but "VR" was wrong at a certain point, leading back
towards the opamp ( I think RG and Analog Mike put me onto that )
It was indeed the JRC4558 that was at fault !
While I was "in there" I changed all the electro's for new panasonics rated
at 16v
( I put a 4559 back in there .... ssscchhh ..... dont tell anyone !! )

MM.

[dosmun]

Build an audio probe and check the input and output of the Chip.