2270 - Serial 11728 - Refurb, mostly caps and diodes, a few transistors

[Dingman]

This might turn into a re-furb - I have nearly all the parts (caps, diodes, transistors and relay) already. But I can't really find any faults with the unit as it sits, stock.
I've already done the PS\idle\DC adjustments and they all landed right where they should be. I did hit nearly the bottom limit on the pots to get idle adjustment tho (R763).
PS was way high, at 47VDC - adjusted down to 35VDC.
DC was high, 17mv and 24mv. Both adjusted down to 2-3mv.
Idle was high in the 40's mv. Both down to 10mv (across both emitter resistors).

Load test (8.3 ohms) with 250mv into Aux produced about 85 watts, just before clipping.


Square wave is holding nicely at full output, 1Khz

 

[Fairlane]

Very good. Now we need pictures of the 2270.

 

[Dingman]

This is the last pic I have of it, a couple of years old. Paired with a 2440 just for fun. And now, I have two brand spanking new wood cases for them both as well.
I'll post lots of pics of work that is done to it.

 

[KutzlerTrans]

Lookin good Brother!

 

[Fairlane]

 

[Steven Tate]

I would have a hard time cracking into that thing with that kind of performance. I guess a thorough inspection under magnification looking for any sign of leakage or corrosion could change my mind. Nice!

 

[rBuckner]

Hey, as long as you like the sound, why not leave it be if you're keeping it? The cosmetics look great in the pictures so it sure looks like a keeper.

P.S. Nice screen shots of the scope BTW. Are they camera shots or an output of the scope?

 

[Dingman]

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I would have a hard time cracking into that thing with that kind of performance. I guess a thorough inspection under magnification looking for any sign of leakage or corrosion could change my mind. Nice!

Believe me, I'm having the same thoughts. All the adjustments that I've checked (Power supply output, DC offset and idle) all came in right on the money. Sound seems OK on test Klipsch bookshelves. And ya, cosmetics are great.
But I've already bought over $100 worth of parts... Heh, Hmm. I've got another 2270 that's absolutely trashed and not working - I've never really even tested this one, was going to use for parts. Now I'm wondering if that's the one I should try to revive. Thinking...

 

[Dingman]

Hey, as long as you like the sound, why not leave it be if you're keeping it? The cosmetics look great in the pictures so it sure looks like a keeper.

P.S. Nice screen shots of the scope BTW. Are they camera shots or an output of the scope?

That's a good question - I can't complain about the sound at this point. Could it be better? Evidence from others says yes, it could be. But I have to admit, I'm not incredibly picky - once SQ hits a moderate point for me, I'm good. And ya, I'm keeping this one, it's mine, matched to that 2440 for fun - even the lighting between those two units matches perfectly.

Those scope shots are from the USB-to-PC connection from the now common Rigol DS1054Z. Looks like Rigol hit a homer with that scope, at $399, it's performance and functionality is totally adequate for us hobbyists. 4ch digital scope, comes with 4 probes. I'm pretty happy with it, though it seems to exhibit some ghosting on the display, the traces aren't as "smooth" as on the old Tektronix I learned on in school. It's nice you can screenshot all the vitals - waveform, RMS, Freq, P-P - and actually anything else you can think of.

Man, you guys about have me talked into buttoning this good 2270 up. I did actually double up on my parts order (kinda normal for me) and so I could drag out that beat-to-shit ex-party 2270 and see what I can do with that, then keep a full set of parts for the good 2270 in case it ever goes down. I'm going to give it a good visual and then decide.

 

[rBuckner]

Choices, choices....

 

[Chrisxo55441]

maybe you could do just one board, the power supply gets a lot of wear. ive had just that done on a couple of receivers and it seemed to give them a little more kick.

I would have a hard time cracking into that thing with that kind of performance. I guess a thorough inspection under magnification looking for any sign of leakage or corrosion could change my mind. Nice!

Hey Steve did you see that 2440 sitting on top of the 2270? Sweet i love those meters

 

[Steven Tate]

Hey Steve did you see that 2440 sitting on top of the 2270? Sweet i love those meters

Yeah, one of these days......maybe.

 

[KutzlerTrans]

I second freshening up the Power Supply. I would also suggest buying new mica insulators and a good non-conductive heat sink grease and cleaning and re-applying it to the output transistors.
That will help keep it running cool and stable.

 

[Dingman]

I second freshening up the Power Supply. I would also suggest buying new mica insulators and a good non-conductive heat sink grease and cleaning and re-applying it to the output transistors.
That will help keep it running cool and stable.

OK, that's what I'll do then. I'll do a nice job on the power supply and then button it back up. That's a good way to add something useful to this thread, heh.
I'll be ready for more if it ever exhibits any issues.

 

[Dingman]

My remaining parts (am I the only one that can never seem to get ALL the correct parts on one order?) should be here shortly, so I started on this PS board. I still have more to get out, obviously - about 3\4 done I think (depending on how many resistors get replaced).
I'm going to change out the carbon resistors, the little diodes, the relay, all the lytics'. Then clean the board as best I can without removal. Oh, I forgot that variable resistor - dingit. Hmmm.
No reason (unless you guys correct me) to change the ceramics or the bigger diodes? No transistors looks like problems, that I can see? Any other suggestions\tips?

 

[Dingman]

Making progress (I'm a little slow - that whole job thing, you know)
Using an Omron MY2N-DC24(S) - looks to be a prefect replacement.

 

[Dingman]

I don't know about y'all - but I always try to get the pads fairly clean, and then bend the leads over in an attempt to get a mechanical connection rather than relying on just the solder. Obviously, I don't always succeed and maybe I hit 50% for mechanical connections. I also believe the bend helps with stability, the support of the caps, even if they are smaller. And ya, you can see I scratch the board accidentally sometimes - I hate it but I can't always stop it. That happens when I'm using the dental pick to straighten the leads on the components coming out.

 

[Steven Tate]

That happens when I'm using the dental pick to straighten the leads on the components coming out.

That’s ok. I slip in peoples mouths all the time. I’ve just learned not to say oops!

 

[Dingman]

That’s ok. I slip in peoples mouths all the time. I’ve just learned not to say oops!

LOL , so I take it that you are a dentist? Heh, you are correct, no one wants to hear "oops" when in that situation!

What do you think about replacing those ceramics in the power supply? I normally don't change ceramics, seems like they rarely are in the signal path - but never really thought about the ones in the power supply before.

 

[Steven Tate]

LOL , so I take it that you are a dentist? Heh, you are correct, no one wants to hear "oops" when in that situation!

Yep. Guilty. As for the ceramics, I’m no expert, but mostly The recommendations I see say to leave them alone unless they are known bad. I have seen occasional recommendations in certain applications to replace small ceramics with C0G rated ceramics, which if I understand correctly, are more temperature stable than the originals.