How to test a Bi-Directional Triode Thyristor

[Tom.G]

I have added a link in the OP. Which old links/attachments should now be removed?

Thanks!

Link in post 131, and copied in 134, is valid but points to an outside repository. You should probably contact owner of post 131 for his desired resolution.

For my post 134 (referencing 131), I don't like to remove a 'job well done' comment but it gets confusing to leave it as is. I will leave the final determination to you and post 131 owner.

My post 130. At your discretion, the second quote thru end of message may be deleted. This may avoid possible confusion for those trying to follow this mess in the future.

And this post itself can confuse the heck out of folks, but I couldn't find how to PM you. Maybe it too should be deleted.

 

[Planobilly]

I would delete post 131 but I don't know how you do da!

Anyone who can delete stuff can delete anything I posted without issue and this post also when we get this mess cleaned up!

I know the internet is a strange place but I am not one of those people who get upset about much of anything. Well...there is that big fish I lost...lol

Cheers,

Billy

 

[jim hardy]

Hmmm I'm slow but the lights are beginning to twinkle on.

So SVR301 adjusts the regulator that fires triac... they tell us to adjust by measuring the 100 volt line
but the regulator senses 4 voltages, ±60, -100 and i think +100...

Pin 5 should be about -1.3 volts because of a milliamp each thru R308 and R310 from -100 and -60 volt supplies
so pin6 must be driven to match pin5
junction of R309-R311-R313 should be similarly around +1.3 because of a milliamp each through R309 and R311
(though i haven't yet found how +100 gets to R309)

that suggests around a half milliamp entering pin 6's node through R305, 2.6V/5.1K = ~.5ma
and that half milliamp has to exit the node through R306-SVR301
so there's our balance ... ZD301 is voltage reference against which supply voltage is balanced.

I submit -
If + supply voltage increases, that makes pin6 more positive, lowering opamp output,
and that decreases current through R301 and photodiode
retarding Triac firing angle to restore voltage...
That's the closed loop ?
R303-D302-C301 allows regulator to raise voltage faster than it can lower voltage
D301 protects the photodiode against reverse voltage (it's only rated 5 volts reverse)

What signal comes in through R332-D308 i haven't figured out yet.

Anybody else know ? I'm a plodder, as you know..

whew out for tonite

 

[dlgoff]

Anybody else know ?

Looks like the right and left audio out is summed and supplied to that regulator and also to LED vu meter. Must be giving the supply a little kick at higher volumes.

 

[Tom.G]

What signal comes in through R332-D308 i haven't figured out yet.

Feeds back speaker voltages via R327, 328 and output stage current (around 12A peak) via (left chnl.) R211, 213, Q113, 115, 301. These are combined in IC301. If I got the polarity inversions right, this shows up as a negative feedback to the Triac ckt. The speaker voltages seem to be pretty much a linear feedback, and the output stage current more of a hard current limit function, both with some time delay/averaging from the IC301 outputs.

 

[jim hardy]

If I got the polarity inversions right, this shows up as a negative feedback to the Triac ckt.

Thanks !

You are quicker than me. I only just now found "MP101" which carries speaker current signal over to upper left corner...
Now i see what they mean by "multiplex" power supply -
that mess surrounding Q127, Q129, Q133 and Q137...
too many frills for my taste.

I'll keep plugging.

Have you figured out what advances firing during high power?

 

[Tom.G]

which carries speaker current signal over to upper left corner...

That negative speaker current feedback might be for speaker damping, but I'm not sure.

Have you figured out what advances firing during high power?

I think you pretty much nailed it in your post #143. If any DC supply voltage drops below nominal, the Triac phase angle is advanced. fires earlier.

that mess surrounding Q127, Q129, Q133 and Q137...

Here's my take on it.

Left Chnl:
Q127, 129 Audio Output stage.
Supplied by:
idle D127 (30V supply);
at higher audio input levels Q131, 133, D125 (60V supply);
at speaker >+52V_PK Q139, 143, 145 (then thru Q131, 133) (100V supply)

Q113 is current limit for output stage with fast clamping at 25A peak.

BTW:
The 100V supply is used only above 320W_PK into an 8 Ohm speaker. (WOW!)
Except for C101 0.47uF at the RCA input jacks, the whole rest of the amplifier is DC coupled. (Need a decent servo amp for something?)

 

[Ralph Dratman]

This thread reminds me of browsing TV repair anecdotes and tricks in Popular Electronics circa 1963, when I was 12 years old. The shop lingo was exotic. "Back porch", "color burst", "horizontal sweep", "video amplifier", "AGC" and the like all stimulated my imagination, as tales of pirates or race cars might have for un-geeky boys.

 

[Planobilly]

Well Ralph, I will only speak for myself, but I think I may not be the only one on this thread who was actually reading Popular Electronics in 1963. 1963 was a good year as I had a 1963 Chevy Super Sport convertible.

Mine was a different color. In 1963 Tom Wolf published in Esquire magazine something about a "Kandy-Kolored Trangerine-Flaked Streamlined Baby so I just had to paint the car that color.

The sixties in America was a special time and I have fond memories of those times.

Cheers,

Billy

 

[dlgoff]

1963 was a good year as I had a 1963 Chevy Super Sport convertible.

 

[Tom.G]

Referring to posts #146 (by Jim) & #147 (by Tom) above, the speaker current feedback seems to be explained here:

Particularly in the graphs at the bottom of post #5.
Small Amp Project (Tube/power stage info needed)

 

[jim hardy]

Good eye Tom !

I hadn't caught that in the Carver,
i only assumed they used current just to invoke a power limit.

But it's right there on the block diagrams , page 8 of service manual.
And specification page says

Damping Factor Greater than 9 - Tube Characteristics

Thanks !