2270 - a few questions as I near completion

[Osibisa]

Been tending to a recently acquired 2270. Thanks to the knowledge base available on this forum I was able find tips and tricks needed to replace all of the dial lamps, filter and P800 caps.

My question is related to P700, specifically trim pots R708 & R709. I came across two posts that suggested adjusting the collector voltage of H705 & H706 (clipping level) to about 17vdc via R708/R709 after changing "the usual suspects" on this board, but have not seen any other posts or comments about it.

Just want to confirm if this is the correct procedure before I make any changes. The schematic indicates 16.3v should be there and I currently have 14.3 on one and 15.6 on the other.

Second question is related to the FM tuning meter, when in a power off state the needle should be centered correct? Mine is off to the left ever so slightly and it bugs me, haven't looked at the back of the meter for a centering adjustment yet.

Thanks

 

[catrafter]

Those P700 adjustments are not critical, yours are OK.

Have you tried wiping the FM Tuning meter with a 'bounce' dryer sheet to remove any static?
The meter has to be disassembled to get to the power off centering adjustment, not for the faint of heart.


Tom

 

[rBuckner]

^^^ Risky business indeed!

 

[Osibisa]

Ok then, I will leave well enough alone.

How critical though is the replacement of C703 & C704 with electrolytics? I've got new ones and haven't put them in yet, and if I do, will they alter the sound in any way?

 

[Steven Tate]

Those are tantalum capacitors, right? I think most people usually replace them with 22uF/10v electrolytics. Tantalums are considered to be potentially troublesome. I don't think you will hear any sound change.

 

[Osibisa]

Thanks Steven, I think I'll leave them alone for now at least since the 1212's were replaced.
The original 2SC458's were creating noise and all is quiet now.
Next is replacement foam tape for the cover and it's done!

Actually not quite, as I want to do something with the metal cover. Since a black faceplate will be going on I would like to paint or have it powder coated black as well. Probably won't matter since it will be going into an audio cabinet anyway.

 

[Steven Tate]

You will likely be able to see the wood grain metal when it is mounted in a black case. You could either paint it black, or if you wanted to be able to get back to original, remove the metal case, store it and put the unit in the black case naked. It will probably cool better that way anyway.

 

[KutzlerTrans]

Good advice there, Keep it cool by keeping it off, or at least drill lots of vent holes above and below the unit to get rid of that heat. a little computer fan would be nice.

 

[sssboa]

Ok then, I will leave well enough alone.

How critical though is the replacement of C703 & C704 with electrolytics? I've got new ones and haven't put them in yet, and if I do, will they alter the sound in any way?

I just wonder why they used tantalum there and not in other places, if there's some logic to it. From my experience tantalum larger than 2.2uF age well. These measured well in my two 2270s, I even remember, 28uF and decent ESR, but I replaced them anyway, but to new 33uF tantalum that is quite a rare thing to do, I know.

 

[Osibisa]

That's a good point, I'm still on the fence.

Now a new issue was discovered when I connected my components to the receiver.
All inputs operate fine except when I plug cables (RTR & PC) into either of the tape output jacks.
A "popping" sound is heard thru the speakers and headphones whenever the selector is in Phono (either 1 or 2) AND the TT is cycling to or from an album.
Disconnecting the cables from the tape jack brings the receiver back to a quiet state. This is happening with three Dual TT's and only when the Record jacks are occupied.
It doesn't matter if the tape inputs are connected or not. There was a thread a while ago from a member that was experiencing the same problem with his 6300 TT, but I don't think it was ever resolved.

http://audiokarma.org/forums/index.php?threads/rebuilt-2270-phono-popping-on-6300-auto-off.491712/

Since this 2270 is new to me and not my primary I have no idea if this is known issue or not.