Sansui QRX7001 repair

[mandrix]

I looked on Digi-Key and they're definitely NPN

I'm just wondering how he determined they were PNP, if he tested or what, you know.

 

[SPXER]

 

[DuncanS]

It is more likely that the MJ150001 has a different pin-out to the 2SC1111, so Emitter & Base pins are swapped.

 

[SPXER]

I was of the belief that all TO-3 had the same pin-out. From Motorola data sheet...
Sorry, the writing did not show. Anyway, the datasheet shows lower pin in drawing as base, upper pin as emitter, case as collector.

 

[DuncanS]

I was of the belief that all TO-3 had the same pin-out.

I have always checked against a datasheet as I once had an error on a PCB when I didn't give the PCB layout guy the datasheet with the pinout (wasn't a TO-3 though).

The only datasheet I have found is for the MJ15001, so your metering is correct for that as the +Ve (Red) is on the Base & GND on the Emitter, so the B-E diode conducts. For the MJ part the pin out orientation is set by the package markings.

If you rotate the 2SC1111 through 180degrees and applied the probes, you should see the same response as the MJ15001. I found this bottom view of a 2SC1111 on line. transistor 2SC1111 datasheet

 

[SPXER]

It does not read as NPN in any combination. I believe they are counterfeits. And bad ones at that. I will try to get a refund.

 

[SPXER]

A question about listening to 4-channel music. Does one have the sound level the same on the front and back speakers, or are the back speakers usually set at a lower level?

 

[mandrix]

Calibrate to taste.

 

[SPXER]

So., what is your taste, mandrix? Anyone else care to share? I have a reason for asking. I may reveal later on.

 

[Owen Smith]

Personally I calibrate the rears to have exactly the same volume as the fronts. This is done using test tones generated by the amp or a test DVD/blu ray, and a sound pressure level meter to read the levels and then change the channel gains to make them all the same. Most (all?) content assumes the speaker levels are set like that.

 

[mandrix]

So., what is your taste, mandrix? Anyone else care to share? I have a reason for asking. I may reveal later on.

I use Dirac Live and a 13 point mic placement for tightly focused seating area (desk chair). My audio room is a bedroom about 8.5' x 12.5'.
My speaker configuration is 7.1.4.

When I had a true Quad setup 50 years ago or so I tried to place the speakers equidistant from the sweet spot.

 

[jupp369]

I have always checked against a datasheet as I once had an error on a PCB when I didn't give the PCB layout guy the datasheet with the pinout (wasn't a TO-3 though).

Take a good look at the circuit, see where is NPN or PNP and where are E C B and compare with what you have! ...or you might blow it up!
anyone make his own pinout ..

 

[Owen Smith]

If you are looking for parts for this restoration, QRXRestore sell some:

https://www.qrxrestore.com/parts/

 

[jupp369]

So., what is your taste, mandrix? Anyone else care to share? I have a reason for asking. I may reveal later on.

Luckily I've now a 6x6m room with the couch in the center = optimal. So 4 equal Speakers at the same volumen.
(4 equal Speakers should always be mandatory because of the frequency respose. Later you can use them also in a 5.1 system)
I'm also using 4 analog VU meters to see what's coming out - the amplifiers are not so well as told by the salesmen, have to correct the potis.

 

[DuncanS]

Take a good look at the circuit, see where is NPN or PNP and where are E C B and compare with what you have! ...or you might blow it up!
anyone make his own pinout ..

I'm an Electronics Design Engineer and even with all the technical documents mistakes get made! In the case I mentioned, as a Junior Engineer (many many decades ago!) I didn't check the PCB layout sufficiently, and then had to explain to my boss why we had to re-spin the board. I was not popular.

 

[mandrix]

I worked for a company that made boards for the telecom industry. Pretty primitive by today's standards I guess. I identified the problem(s) and handed them off to my co worker who did all the soldering/de soldering.
Saw some strange stuff I never could figure out. Sometimes I'd have my co worker just replace every IC on the board. lol.
We got 99 boards back from one company that puked, and my boss was pissed that I could not repair any over two days and very publicly chewed me out. So he spent a whole day working on them and got one board to work one time. lol.
One signal kept hitting the AND gate before another one (IIRC) and he tried everything in the world to fix it and NADA.

Sorry if I'm going off track here....

 

[barfle]

A question about listening to 4-channel music. Does one have the sound level the same on the front and back speakers, or are the back speakers usually set at a lower level?

Generally, the recommendation is that all channels are equal - same amps, same speakers, same levels. There are a few purists (not a bad thing) who can achieve that setup, but I have never had that many of the same speakers or amp channels to do that, and I still love listening to surround sound (well, most of the time).

 

[MidiMagic]

I once had a VOM with the ohms polarity backwards from most VOMs.

 

[mandrix]

Well my corner speakers are matched. My overhead speakers are matched, though not with the corners. My side surrounds are another type speaker.
My listening position, by necessity, is about, guessing, 4 ft to the rear of the center of the room. My side surrounds are just forward of me.
All speakers point directly at the listening position, save the sub of course.
I have a 29 inch monitor directly in front of me, just below the bottom level of the fronts.
Crazy, but is what it is.
I can't say it would work for everyone, and the calibrations will be retuned when I get my primary AVR back from the shop.
But, I can't emphasize too much how Dirac Live, through the pc app, has helped this crazy room. With a few needed adjustments.

 

[par4ken]

I ordered a set of 10 Motorola MJ15001 to replace the shorted 2SC1111 trans. Checking the Mj15001's they read as PNP, not NPN as the 2SC1111,s. All the literature on the MJ15001's show them to be NPN. Is there an explanation for this? Mislabeled?
I am disappointed for sure, as I can't put the QRX back together.

The MJ15001 should be suitable. You could be right the one that you have might be mislabelled MJ15002's.
There are lots of actual 2SC1111's available for sale on eBay.

The data sheet for the 2SC1111 shows the same pinout as for the MJ15001.