How to test a Bi-Directional Triode Thyristor

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The discussion revolves around troubleshooting a Carver model M-1.0t stereo amplifier, specifically focusing on testing a Bi-Directional Triode Thyristor (triac) that controls the AC input to the transformer. Participants suggest various testing methods, including measuring gate voltage across R409 and using a light bulb in series to observe the triac's behavior. There is a consensus that the triac regulates power and may act as a safety feature, with concerns about potential faults downstream in the amplifier. Suggestions include checking the transformer output and considering the triac's replacement with a modern equivalent. The conversation highlights the complexity of the circuit design and the importance of careful testing to avoid further damage.
  • #101
Thanks Tom -
i may have missed a tie point. That makes sense now.
carver12.jpg
 
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  • #102
While 100V secondary lifted: 100 volt filter caps both good ? 100V Bridge ? Winding not grounded ?
 
  • #103
Hi Jim,
In reading the many things that have been said both here and on other forums, it is clear that there are many opinions as to how this amp works. I am most likely the least qualified to make any determination on my own. I also do not understand the heavy black lines. It is also hard to read this schematic for many reasons. The symbol for the triac did not look like anything I had seen before, nor have I find found one just like it elsewhere. Perhaps it is normal and just not known to me.

I will have to do some digging to find out where and how the 100V supply gets to things.I have all the electrolytics removed from the amp at the moment. When I get the parts and things back to normal I will continue the troubleshooting.

As far as the transformer goes there are only three wires going in and six wires coming out. Two each on the secondary for the three voltages and two wires on the primary from the mains, one going through the triac. Also one wire from the thermal safety device. I have not removed the transformer so I guess something could be in a place I can not see but I don't think so. I do not think there is anything special about this transformer as far as I can see at the moment. Someone would need to put me up to speed on how DC could be used to control a transformer in the first place. At the end of the day, three AC voltages come out of the secondary 30V, 60V, and 100V and go to the three bridge rectifiers providing positive and negative supply voltages.

I got the idea from some post that the triac (or what ever was controlling the triac) was not only controlling the timing of the AC but was controlling the voltage to the transformer. I have no idea how that could be possible. Perhaps when I get the book you recommended I will have a better idea of what a triac can be used for. Where ever I got the idea I remember that person saying the voltage to the primary was about 40V. I did not measure the voltage to the primary. I measured the voltage on the secondary after I removed the 100V connection from the transformer to the rectifier. At that time I was not comfortable letting things being powered up and only made a few quick measurements.

And Don...I had given the shotgun approach some thought...but more along the lines of using my 12 gauge on the amp...lol

Cheers,

Billy
 
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  • #104
Thanks Tom...good eye!
 
  • #105
jim hardy said:
While 100V secondary lifted: 100 volt filter caps both good ? 100V Bridge ? Winding not grounded ?

I removed and am replacing all the filter caps Jim. Also 100V windings are good.
 
  • #106
Planobilly said:
The symbol for the triac did not look like anything I had seen before, nor have I find found one just like it elsewhere. Perhaps it is normal and just not known to me.
Meh,
i'd call it an Andy Warhol Edit oops make that Salvador Dali - triac.
 
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  • #107
Planobilly said:
Someone would need to put me up to speed on how DC could be used to control a transformer in the first place.
When you're ready to go there start a search on Magnetic Amplifier. Dont worry this isn't one.

Planobilly said:
I got the idea from some post that the triac (or what ever was controlling the triac) was not only controlling the timing of the AC but was controlling the voltage to the transformer. I have no idea how that could be possible.

When you chop out part of the wave you are controlling the voltage.
Shaded are is where conduction is going on
carver13.jpg

actually, conduction into the caps stops when they've charged , before zero crossing.
Mr Carver's artist was not an electronics guy.
Point is, when there's no conduction, before triac gets fired, there's no voltage applied to the transformer.
That is called "Phase Control ". Your SCR manual has a chapter on it.

Remember "average value" is the area under the curve ?
Firing triac earlier or later in the cycle varies the shaded area. So the average value of voltage is controlled.
This is just a lamp dimmer with electronically adjusted knob, the knob being current through the optocoupler.

Remember - Triac is a just a snap action switch , a very fast one like only a few microseconds to turn on .
Gate current turns it on.
Remove gate current and it stays turned on until current through it falls to almost zero. That happens at or near sinewave zero crossing.
 
  • #108
Thanks Jim,

I went to bed last night thinking about this. I then remembered what the phase angle could be so I now see how the voltage is reduced.

Thanks,

Billy
 
  • #109
Planobilly said:
I went to bed last night thinking about this.

Our mind settles a lot of things in our sleep. And in the shower, for me ...

Congratulations - we learn fastest by simultaneous doing & studying, don't we ?
 
  • #111
  • #112
You know you are dealing with a strange amp when Salvador Dali's name gets mixed up in the conversation...lol
 
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  • #113
TomG cleaned up the schematic.
He sent me a copy
But i don't know how to post it, it's a 3.2meg jpg.
Photobucket didn't work , shrunk it down to illegible.

old jim
 
  • #114
Hi Jim,

Perhaps there is no way to post such a large file here on the forum.

I also received a schematic from Mesa Boogie for the Nomad 45 guitar amp via email that I do not know how to post here. Actually there is no new information on the schematic except for a mod to the amp which we really don't need.

Still do not have the parts yet for the Carver or the Mesa. I guess if one had a 10,000 sq foot room filled with parts there would always be something missing...LOL

I did not grow up in this internet world so I am always having issues trying to post stuff. We all need a couple of nine year old kids to show us the way..!..LOL

Cheers,

Billy
 
  • #115
Jim, can your large image be cropped somewhat, and then uploaded? I think the upload limit is around 3 MB
 
  • #116
NascentOxygen said:
Jim, can your large image be cropped somewhat, and then uploaded? I think the upload limit is around 3 MB
Dang. I just logged into catch up on this thread and was going to suggest just that. You're putting out some fairly strong bran waves I guess. :bugeye:
 
  • #117
jim hardy said:
TomG cleaned up the schematic.
He sent me a copy
But i don't know how to post it, it's a 3.2meg jpg.
Photobucket didn't work , shrunk it down to illegible.

old jim

It's a PDF, using ZIP compression internally. I didn't use JPG because that loses details during compression.

I'll try some tight cropping and see what happens.
 
  • #118
Here it is cropped and resized to 50%
still about two screens wide
further reduction is too small to see

and it gets autoshrunk (by forum software i guess) to one screen wide , which is a good thing, keeps it from wrecking the thread - see feedback forums thread on that subject.Image removed to save disk space
 
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  • #119
Tom.G said:
It's a PDF, using ZIP compression internally. I didn't use JPG because that loses details during compression.

Yes i was able to "copy image" and paste into paint, save as jpg... Sorry for the mis-information.
 
  • #120
It might be better to leave it as a thumbnail, not display it inside the post, then readers (those who want to see the detail) can open the image in a separate browser tab and magnify it to heart's content.
 
  • #121
NascentOxygen said:
It might be better to leave it as a thumbnail, not display it inside the post, then readers (those who want to see the detail) can open the image in a separate browser tab and magnify it to heart's content.
What a good idea !
I'll remove that last post and try it.
Here's the cropped one, 2.96 mb. Thumbnail only.
Edit - removed unneeded image to save disk

I'll go remove that last one now, to save 3 megs of magnetized iron oxide .

Hmmmmm looks like it gets downsized to 960 pixels anyway
shrunk from 2.96 megs to 207.7K during "Upload"
 
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  • #122
That works well.

I can download the file and work with it as I like.

Thanks,

Billy
 
  • #123
Members who don't use a tablet could be forgiven for assuming that when using a tablet we can just keep spreading the image to magnify it almost without limit. Not so, at least not on my Android 4.4

Well before a small image like this schematic becomes readable, the PF page headers MENU, MY PF, INBOX, etc., enlarge and move down to cover over the viewing area!
:H:H:H

I must instead open the pic in its own browser window.
 
  • #124
Just to clarify the situation a bit:
NascentOxygen said:
It might be better to leave it as a thumbnail, not display it inside the post, then readers (those who want to see the detail) can open the image in a separate browser tab and magnify it to heart's content.
That would be fine, even tablets have PDF readers. HOWEVER I can't find a way to post the full size PDF. Compressing and zooming doesn't work because the readability/detail is lost in the compression, and zooming something that isn't there doesn't help.

The original page size of the image was roughly 8.5x11 but if the resolution is taken below about 360 DPI the small printing and details, like whether a transistor is NPN or PNP, are lost.

EDIT: You guys are fast! The time it took me to write this, there were four more posts.
 
  • #125
Tom.G said:
I can't find a way to post the full size PDF. Compressing and zooming doesn't work because the readability/detail is lost in the compression, and zooming something that isn't there doesn't help.
Correct, but you're running up against our 3MB attachment limit? If you need to make available a file larger than that limit, the only way is to store it on an outside host (of which there are many available for free) and to include the URL in your PF post.

The big drawback in using a hosting site is that at some future stage it's likely that either you or the host will drop the file, and then the PF thread of which it was an integral part becomes next to worthless.
 
  • #126
Planobilly said:
That works well.

I can download the file and work with it as I like.

Thanks,

Billy

It's not as clear as Tom G's rendition
i'll email that to you
 
  • #127
Thanks Jim

I assume there is some site somewhere that PDF's can be stored on that anyone can access. I am looking now.
 
  • #130
NascentOxygen said:
Correct, but you're running up against our 3MB attachment limit?
I must have missed the 3MB limit. All I saw was image limit of some pixel count. If your file size limit is 3MB I'll see what tricks I can figure out to get there.
 
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  • #132
If the upload is successful at 2.998MB, here is the enhanced Carver M1 schematic in PDF format.
 

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  • #133
Tom.G said:
If the upload is successful at 2.998MB, here is the enhanced Carver M1 schematic in PDF format.

Works great - You 'da Man !
 
  • #134
  • #135
I guess the only thing remaining for this side issue is to get a link in or near the OP, rather than buried 7 pages deep.
 
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  • #136
Now if we could just get schematics that actually tell us what we want to know!...lol

I am off to bed.

Cheers,

Billy
 
  • #137
If only!

All my Wizard contacts have either died or left town.
 
  • #138
Tom.G said:
I guess the only thing remaining for this side issue is to get a link in or near the OP, rather than buried 7 pages deep.
I have added a link in the OP. Which old links/attachments should now be removed?
 
  • #139
i cleared out mine, hope i got 'em all.
 
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  • #140
I will be out till this afternoon.

Billy
 
  • #141
NascentOxygen said:
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.
 
  • #142
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
 
  • #143
Hmmm I'm slow but the lights are beginning to twinkle on.

upload_2016-4-14_20-40-5.png

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...
carver14.jpg

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
 
  • #144
jim hardy said:
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.
 
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  • #145
jim hardy said:
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.
 
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  • #146
Tom.G said:
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?
 
  • #147
jim hardy said:
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.

jim hardy said:
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.

jim hardy said:
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 >+52VPK 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 320WPK 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?)
 
  • #148
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.
 
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  • #149
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.
h7xVmJC.jpg

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
 
  • #150
Planobilly said:
1963 was a good year as I had a 1963 Chevy Super Sport convertible.
 

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