This Is Ridiculous, Scott R-316 AC Problem

[Jeff Urban]

Print is available on hifiengine. This is one that has that multi voltage switching. Not getting anything. Something happened, I Tshot this thing a while back and it was a no rush, but now comes time to get it the hell outta here. I got the parts for a blown channel, put them in and dead. Actually I am relearning how to read those old PC boards. It is coming back.

So this one, I got continuity from the cord all the way to the voltage selector. That rules out the switch and any and all fusible devices in the way. testing for actual AC is easier said than done but if you got continuity it must be there, right ?

The transformer has the usual dual primaries so the odds of that being open are not high, especially both of them. And then to cut to the chase I got me a suicide cord and injected the AC straight into the one primary and got at least dial lights where before I had nothing.

Then I checked the plug for the selector and it has continuity where the print says it should.

Forty fucking years in the business and this stupid ass thing is driving me nuts(er). If I get sick of it I will figure out how to just permanently wire it for 120 volts and be done with it but I would rather not. If I can avoid it.

This is ridiculous, I have figured out the rewire on a bunch of PX type of equipment. (multi voltage) Like SAE when nobody could get q print, and Marantz that wouldn't give out the information to anyone but authorized service.. Piece of cake. But this damn thing...

I even pulled on the wires on the jack for the voltage selection to see if maybe the copper inside was broken.

There would have to be two thermals out in the primaries for this, unless maybe one in the secondary but it is center tapped and shows continuity.

Another one of those things with nothing wrong but it doesn't work.

So I a willing to at least listen to some flippant ideas in case someone has a buzz on. This is one of those off the wall things, really.

 

[pfjw@aol.com]

Continuity via a VOM is only an indicator, not proof-of-goodness. On a great many more than just a few occasions, I have gotten continuity at tester-voltages, but a line voltage - nothing. And that is where your concept of a 'thermal' issue comes into play. Especially with transformers.

Of course there is always the kill-or-cure spark-off - Obtain a high-value, high voltage cap and get it fully charged, this is where an old-fashioned full-voltage cap tester becomes handy. Discharge it into the suspect winding. It just might fuse that thermal failure. I have done this three (3) times, and it worked 2/3 times. The third time, the cap did discharge, but the result was 'open' even with the tester.

Peter Wieck
Melrose Park, PA

 

[Ralph Mowery]

In article <1df8cc21-cc38-47d7-98c1-d18644c964a3@googlegroups.com>,
jurb6006@gmail.com says...

o this one, I got continuity from the cord all the way to the voltage selector. That rules out the switch and any and all fusible devices in the way. testing for actual AC is easier said than done but if you got continuity it must be there, right ?

The transformer has the usual dual primaries so the odds of that being open are not high, especially both of them. And then to cut to the chase I got me a suicide cord and injected the AC straight into the one primary and got at least dial lights where before I had nothing.

Then I checked the plug for the selector and it has continuity where the print says it should.

Forty fucking years in the business and this stupid ass thing is driving me nuts(er). If I get sick of it I will figure out how to just permanently wire it for 120 volts and be done with it but I would rather not. If I can avoid it.

This is ridiculous, I have figured out the rewire on a bunch of PX type of equipment. (multi voltage) Like SAE when nobody could get q print, and Marantz that wouldn't give out the information to anyone but authorized service. Piece of cake. But this damn thing...

I even pulled on the wires on the jack for the voltage selection to see if maybe the copper inside was broken.

There would have to be two thermals out in the primaries for this, unless maybe one in the secondary but it is center tapped and shows continuity.

Another one of those things with nothing wrong but it doesn't work.

So I a willing to at least listen to some flippant ideas in case someone has a buzz on. This is one of those off the wall things, really.

You did not by any chance reverse some of the transformer wires where
they are phased so they cancel each other out ?

Put the ohm meter away and check for voltage with an analog meter.

 

[John-Del]

Don't take this wrong Jeff, but any chance it has a small standby transformer that drives a relay with contacts in the primary side of the main XFR?

Hey, we all brain fart these things on occasion.

 

[Phil Allison]

Ralph Mowery wrote:

---------------------

You did not by any chance reverse some of the transformer wires where
they are phased so they cancel each other out ?


** Reverse connected primaries only ever results in no magnetising in the transformer core. You are then left with just the copper resistance.

Any attempt to operate it under that condition causes a HUGE AC supply current to flow - similar to that during an inrush surge.

Fuses will splat, breakers will trip.



..... Phil

 

[Jeff Urban]

It was so stupid I don't want to mention it. I read it wrong.

So back to the amp. Man, these funky old PC boards, and sometimes marked wrong and sometimes marked ambiguously. But there is no excuse for Q806 or whatever to be marked wrong - you guys designed the thing !

This one however did not have mistakes on the print.
Small favors...

Next thing is the bias, I have to dig up a transistor, I know I got it. That and a couple resistors and I am outta this thing.

i have to raise my rates on shit like this. It is not big power so it is hard to get alot of money. And in some cases even though I got some of the best high power outputs out there, in a lower power unit it is not always appropriate to use them. Not only is it a waste but you might not bet into the thick of the gain curve.

But I do got some gold. I got real JFETs, both polarities. They can do things depletion mode MOSFETs cannot.

So ow all I need is a bipolar NPN with the base in the middle that maintains its hfe at low Vce.

Day in the life.

 

[Tim R]

On Wednesday, April 8, 2020 at 1:51:49 PM UTC-4, pf...@aol.com wrote:

Of course there is always the kill-or-cure spark-off - Obtain a high-value, high voltage cap and get it fully charged, this is where an old-fashioned full-voltage cap tester becomes handy. Discharge it into the suspect winding. It just might fuse that thermal failure. I have done this three (3) times, and it worked 2/3 times. The third time, the cap did discharge, but the result was 'open' even with the tester.

Peter Wieck
Melrose Park, PA

Did this once by accident, trying to locate a break in an underground power line. We were using a thumper and listening to it "thump," then it faded and the line started working again, must have welded itself across the break.