SWTPC Tiger .01 207B Schematic - diyAudio
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Old 2nd September 2009, 01:39 AM   #1
PB2 is offline PB2  United States
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Default SWTPC Tiger .01 207B Schematic

A member asked for this schematic, so here it is:
http://baselaudiolabs.googlepages.com/TIGER-01-207B.pdf

Hope it helps to repair the amp, I've never worked on one myself.

Pete B.
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Old 2nd September 2009, 01:54 AM   #2
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Here it is online, wish I had found this before I scanned it, LOL.
I think this is the A version and the one I scanned is the B, not sure of the differences:
http://www.swtpc.com/mholley/RadioEl...RE_Mar1973.htm
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Old 20th May 2011, 06:51 PM   #3
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Very good! I've got a couple of 207s here which I'll try updating. I also have a blank board which I'll stuff as a repair/experiment unit--possibly the last ever 207 to be assembled?

I installed MJ21193/4s in one and think I see a reduction in high-order distortion products. I can measure as low as .005% distortion at a one watt level, but of course it rises with power and tends exhibit significant high-order products above 5 or so watts. Careful adjustment of bias while monitoring the Tek AA501's output on a 'scope can help to minimize this problem; I'm curious to see what the change in the feedback network may have on this issue?

Anyone tried modifications to SWTPC amps, especially the 207 and Tigersaurus?
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Old 26th May 2011, 02:41 AM   #4
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I scratch built several of the Tiger amps years ago as a kid and always wondered why many of them blew up. I've not looked carefully at the real hardware for probably more than 30 years now but I do plan to take a look, perhaps when I retire, LOL! Something that I always noticed was that the output signal would go very close to the rail, which means deep into saturation. This is because the driver has more voltage (Vce) to work with than say a typical EF type of configuration. This is good for using all the voltage available from the rail, good for efficiency lets say. However, BJTs become VERY slow when deep in saturation and I'm fairly certain that this leads to severe cross conduction and they might even become unstable due to the slow down. I've often seen the capacitors melt in the output stage. I've seen cross conduction peaks in simulation of 2 amps or so. These amps are dangerous for this reason and I would not use them unless you could be sure to protect your speakers in some way. Perhaps reduce the fuse sizes. I considered clamping the drivers/outputs to avoid saturation but was unable to come up with a simple, low parts count solution. A thought just came to me, perhaps reduce the output BE resistor from 100 ohms down to 22 or even 10 ohms, then use something like the MJE15032/33 as drivers that can provide the current to drive that low R. The low resistance might turn them off fast enough, but it would take some analysis/experimentation.
You're probably aware that most poweramps with BJT outputs are not intended to provide full power into clipping for extended periods of time at HF due to this very reason, certainly not above 20 KHz. This is because the cross conduction duration becomes a significant length of time as compared to the period of the waveform.
My experience has mainly been with the Universal Tiger and Tigersaurus both of which I built from scratch, I also built the kit version of the Universal and repaired it probably 3 or 4 times after it blew up.
I had a lot of hope for these amps over the years, but now after seeing the cross conduction I'm not so sure.
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Last edited by PB2; 26th May 2011 at 02:47 AM.
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Old 26th May 2011, 02:56 AM   #5
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The only time I've blown up my home-brew Tiger is on the test bench. They won't stand big voltage swings at 20kHz or more. In music service the thing has been indestructible for about 30 years or so.
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Old 26th May 2011, 03:03 AM   #6
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Yes our kit built version of the Universal Tiger also blew up on the bench but we were not driving it hard, just sitting there with a signal generator connected. It also blew up under music conditions when driven hard a bit into clipping. This same amp did not blow up again for 20 years or so when used in light duty probably never seeing more than 20W out. This was the stereo version with less heat sink and no thermal cutout. My scratch built versions never blew up, but both ran on slightly lower supply voltages so perhaps that is part of it also. I also had figured out by then that the 100 ohm resistors needed to be 1-2W. And I did not try to use them as bench amps, that is for sure.

It certainly is not a bench amp, LOL! But there is something seriously wrong with it given all the reports of blow ups.

People also talk of them blowing up when they plug or unplug the input forgetting to turn it off. I've seen one with a note on top to that effect, LOL!

Damon, did you notice this thread: Universal Tiger

Some of the SPICE work that I did can be downloaded here: Swtpc Universal Tiger Improved And Simulation
I would include Bob Cordell's spice model file and replace all of the bad models with his.
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Last edited by PB2; 26th May 2011 at 03:25 AM.
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Old 26th May 2011, 04:16 AM   #7
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I just added a new LtSpice simulation file at that link that includes Bob Cordell's models. I the old simulation to include reasonable selections from Bob's file. The sim shows 3A cross conduction peaks when clipping at 20 KHz. The zip file includes everything that's needed to run the sim under a standard LtSpice install.
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Old 26th April 2012, 07:57 AM   #8
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this is old in a way .... but here is what i ve seen

if you look at the original application notes or built info original as was for the tiger 01 it seems that the way is made especially regarding ground distribution , pcb , and wiring between transistors is a complete nightmare .

I am pretty sure that any amplifier constructed like this will have serious stability /oscillation problems .

It could be very interesting to look at the simulation results see if there is any trouble there and then clone the amp with modern devices proper compensation and a new pcb without all these problems .

since i don't run simulators PB2 here you jump in !!!!

Again i think that at the time nobody was cloning Tiger 0.1 or one may copy it as was so mistakes made where simply repeated so also here is how these amplifiers have a failure history ...

I rebuilt one of them as we speak but i am also trying to correct the building mess I will try to keep everything original except the building /ground / distribution errors

kind regards
sakis
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Old 13th January 2013, 08:59 PM   #9
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Hello All,

This thread still active?

New to this site. Was just Googling “swtpc tiger 01”. Found this Thread, so I joined so I could post. I purchased (4) Tiger 01’s in 1976 (Quad Era, lol), Built the kits myself, and beyond a bad Clamp Transistor Q17, (# SS1123) in one Amp, new from the Factory, I have never had an issue with these amps. I’ve never even had to open them up (be curious to see how well my soldering actually looks , lol). I originally set the bias using an Intermodulation Distortion Meter.

These have been the Power for my "Stereo” System now for 37 years. Still Kicks. Not debating that these amps may have issues. I just haven’t ever experienced that. Best Audio Investment I EVER made (OK, getting rid of my turntable & going with CD’s / MP3 player was the best fidelity advancement, but that COST a lot more).

Piping in here because, as I have these, I’m interested in other's experiences with them. Not a lot about these posted anywhere, beyond the occasional ebay listings.

As “Rock & Roll” Implies, I CRANK ‘em.
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Old 13th January 2013, 09:57 PM   #10
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Quote:
Originally Posted by Rock and Roll Guy View Post
This thread still active?
I don't think this Forum gives awards for "Thread Necromancy" - I've seen some much larger gaps between posts on some threads.

Quote:
. . . I’m interested in other's experiences with them. Not a lot about these posted anywhere, beyond the occasional ebay listings.
Those designs were real popular in the late 1960's and 70's. I have stumbled across the Popular Electronics articles from time to time on the 'net, and I'm sure you can get microfilm copies from a decent public library.

I recall building the "Lil Tiger" circa 1968, used it to boost some pocket-sized transistor radios to decent volume, then started some experiments and modifications to try understanding how it worked until it didn't work any more. About 1971 used one of the "Tiger" series as the modulation amplifier for a college dorm AM radio station. I think we had to add a few capacitors to keep the RF from upsetting the biasing. Shortly after, I tried building one of the higher power Tiger amps but it was plagued with instability and gave up after going through 3 or 4 sets of output transistors.

Dale
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