TS-808 is alive!!! Sort of...

[Danny G]

Okay.  I recently posted because my newly built TS-808 was dead.  Simply dead.  Someone suggested replacing the OpAmp.  I have 2 TL072's for a Phase 45 I'm building and heard those would work.

Just to be sure I didn't have the original in backwards, I put the existing Op-Amp in the other way.  Nothing.  Went to remove it and HOLY CRAPO!!!  It burned the shite out of my finger!  It was on 5-10 seconds and generated so much heat that if it wasn't fried before, it was now.

So I put the TL072 in (careful NOT to put that one in backwards), and VOILA!!!  I have a signal coming out when the TS-808 is on!!!  

However...  it is a horribly distorted farty interference sound that vaguely resembles a guitar.  All of the knobs work, but only change the farty tone.  I'm going to buy some more 4558's today.

I quadruple-checked all connections and all components, and got the same results that I had listed in my previous post (TS-808 Help!!!, if you want to look it up).

I'll try some new OpAmps.  Any other suggestions as to remedying the farty tone of my new pedal?

[Fret Wire]

It would be helpful if you gave a link to your other thread, and the other useful info, what schematic (with a link), perf or pcb?

[Athin]

try the audio probe [geofex.com] - see where it gets farty, work from there, maybe the new 4558 will help.

[Danny G]

Old post : http://diystompboxes.com/sboxforum/viewtopic.php?t=23235

I'm about to try some new Op-Amps.  Can I make that audio probe with a standard mono input jack (not enclosed)?

[Fret Wire]

Yes, just wrap it with electrical tape so you don't short anything. Check the pin voltages on the IC and the transistors, then post them. Use a magnifying glass, and make sure the solder pads around the IC arent touching. Check polarity on any electro's, tantalum's, or diodes.

[Danny G]

Update--I just got 2 more 4558's, and NEITHER OF THEM WORK.  I also bought 2 more TL072's, and both produce the farty sound.  I'm taking the non-functioning op-amps back to the shop.

This is getting freaking weird.

I posted the tranny voltages in my last post (should be on the next page).  With the dead 4558 and the farty TL072 the votages were the same.


ARRGGGGGGGGGHHHH!!!!

[RDV]

Sort of hate to say it, but there's probably nothing wrong with the OAs. You've got some sort of wiring or misplaced component, or even layout mistake. I've never found a malfunctioning OA myself, though I'm sure it's happened, it ain't real common. Now the one you turned around which got real hot may not work.

RDV

[Fret Wire]

Post the op-amp voltages.

[petemoore]

DMM beep mode
 Clip one lead to ground
 Use the other lead to find ground pin of  the OA socket
 Insert pin 4 of 'standard' OA into that socket pin.

[R.G.]

You have a wiring error somewhere. Maybe a bad connection, maybe an error you can't see because you are too close to it.

To find your problem, the best and fastest way is to use a voltmeter and measure the DC voltages on all the pins of the active devices. Post those here and one of us can easily pick out what is wrong - or at least where to look.

Your description of the sound is a classic description of misbiasing of an active device.

[Danny G]

Here are some OpAmp voltages.  I'm calling the one next to the circle on top "1" and mapped it out how it looks on the board.

RC4558N--(get no sound at all, tried 3 of them)

1 -- 9.03          8 -- 9.04
2 -- 8.81          7 -- 9.01
3 -- 9.03          6 -- 8.98
4 -- 0 (GND)    5 -- 9.03

TL072 -- (Farty noises)
1 -- 9.02          8 -- 9.04
2 -- 8.81          7 -- 8.98
3 -- 9.03          6 -- 8.95
4 -- 0 (GND)    5 -- 9.02

Dunno if this helps.  I'll try the beep-mode thing.  Here are some of the anomalies I noticed from my last post.  I used the GGG layout and perfed it myself.

I took some readings with the DMM and found some anomalies:

--Got no resistance readings for R9 (10k) and R22(4.7M), even after
swapping them out thinking they were bad.

--On the board, got no DC readings for IC pin to ground, switch lug 3 to C11, and switch lug 5 to C1/R22. All other connections including jumpers showed normal voltage.

The Q readings were:
Q1--E 6.73, B 7.09, C 9.20
Q2--E 6.83, B 7.20, C 9.20

I found I had some misconnections, and that 2 of the Electrolytic caps were in backwards, but fixed those problems long ago.

I've triple checked the wiring to all offboard components and the circuit board. The only mods I did were increasing C3 to 0.22 uf and increasing a resistor value, which I changed back thinking I put the wrong one in.  I put in the original values and socketed them so I can tweak it once it's working.


S.O.S....  Help... me.... S.O.S.... help.... me........

[RDV]

Your voltage divider is not dividing. You should have approximately 1/2 of the supply on pins 1, 2, 3, 5, 6, & 7. Check wiring & component values again.

RDV

[Danny G]

Will do!  Thanks to everyone for all their help.  I'm real anxious to get this thing up and running so I can move on to other projects.

[Danny G]

Oh yeah.  What is a voltage divider?

Also, could I have the tranny's in backwards?  

Just trying to think of anything I might have missed.  I have doublechecked all connnections and part values, but will do so again.

[RDV]

Oh yeah.  What is a voltage divider?

Also, could I have the tranny's in backwards?  

Just trying to think of anything I might have missed.  I have doublechecked all connnections and part values, but will do so again.

From the DIY FAQ:
Power Supply - What is V.R., V.B, VREF, 1/2V+ etc....?

Well, V.R. is voltage reference and 1/2V+ is 1/2 of your most positive voltage (usually 9 volts). Usually they are one and the same and you can typically see V.R. connected to a resistor that connects to the input of an op amp as in the Shaka Braddah 3, The Rat and many others. Basically if you see 4.5V or V.R. or 1/2V+ ( all the same), you find all the places on the schematic that reference the label and connect them together. So all of the places that reference V.R. would connect together; one of the connections actually creates V.R. or 1/2V+. The connection that usually creates V.R. or 1/2V+ aka 4.5V (for a 9V battery) usually is a voltage divider. Typically two identical resistors, one to V+ (such as 9V), the other to ground. The place where they connect is V.R. or 1/2V+.

An example of 1/2V+ also known as V.R., V.B., VREF, 1/2V+ etc...

You could have your transistors in backwards, but that's another isssue. Unless you get you IC voltages right, it'll never work.

RDV

[Danny G]

Sounds like we're getting somwhere!

I get voltage readings of either around 9 or 0 for everything on the board.  I see the part of the circuit board that you're talking about, but haven't noticed anything different I did from from the original layout (GGG layout), yet.

One of the resistors from the voltage divider (R9) is one of the two I couldn't get a resistance reading from (R22 being the other), and swapped it out thinking it was a dead part.  The new one did the same thing.  Think that has anything to do with anything?

How easy are electroliytic caps to blow?  I originally had the 47uf cap in backwards...

Thanks, RDV!

[R.G.]

How easy are electroliytic caps to blow? I originally had the 47uf cap in backwards...

Fairly easy. It's possible that the 47uF is now shorted or open. Pull it out and see if you get half the battery voltage at the junction of the two resistors. If so, you had a bad cap. Replace it before using the thing for signal use.

[Danny G]

Damn, I'm at work right now!  I'll check that cap when i get home.  That wasn't the only electrolytic I installed backwards, I'll have to check the other one...

[RDV]

Did you make your own PCB, or get one from GGG?
In either case, make sure that the jumpers are insulated or at least not touching other traces.

RDV

[Danny G]

Perfed it from GGG.  I'll check the jumpers, too.  Pretty sure they're not touching anything, but I'll re-check.