Does anyone have the 2270 bias and dc offset procedure handy? I'd like to avoid getting the whole service manual as I only need this one page.

Thanks,
Mark

Did anyone ever come up with this as I could use it also.

Thanks ahead of time for any and all replies!

This site has the complete manual for free download:
http://schforfree.seedhost.com/archive/?path=Audio%2FProducts%2FReceivers
They limit the download to one per session, so just copy part 3 for now, that has the procedure:
http://schforfree.seedhost.com/archive/download.php?path=Audio%2FProducts%2FReceivers%2FM arantz_2270_Receiver_Part3.pdf

Thank you very much sir!, Yu da man!

By the way I believe it's a 10 meg limit or 3 downloads per your resetted ip address.
If you start your download before the 10 meg limit it lets you finish that download.
Just for info!

I've been to that sight before and did not notice the 2270 there, again thanks for the link!

Oh yah and with 2 nics in your pc providing 2 addresses you can get all 3, weehee!
If they had a link to subscribe and pay a small paypal fee I would, but they want you
to email someone then they'll get to you, It's probably me but that just bothers me.
See yu!

Can someone please just post the numbers of the trimming resistors and jumpers involved and the ranges. I have my 2270 in the kitchen and taken apart. Thanks.

I tried Dr*Audio's links and they appear to be dead. Attached are the scans from my manual. Please note the misprint involving one of the test points for bias adjustment which I've corrected.

Here are the numbers after adjustment on the Marantz 2270:

L: 0-2 mV fluctuating
R: 0 mV steady

Thanks Ski, could not have done it w/o your help.

anyone have the manual for a kenwood eleven series lll? I need to reset the bias offset etc on this monster. I get 130 and 99 mv on the speaker terminals. I need to know what values they are supposed to be and where the pots and testpoints are. thanks

I'm setting up one of these receivers following the "audio adjustment" procedures posted earlier in this thread. The instructions are very clear but the actual board is cramped and hard to see. I found the test points for the voltage adjustment and the trimmer pots for offset but I can't find a trimmer marked R 763. Are these the other pair of timmers on the same board as R762?

- Pete

According to my foil scan, R763 is the adjust pot closest to the two TO-66 driver transistors, at about the center of the board on the edge. R762 is also on the edge of the board, but mounted towards the end.

Leave the two small trimpots alone. IIRC, these are for adjusting the current limit point (might be wrong, but I'm too lazy to dig out the manual).

I should take a picture to make this simple. The pots for offset are on the edge of the board. They have kind of a built in knob that you can turn by hand. There are an identical pair of these pots right next to the offset pots. I assume those are the bias pots but I can't find an ID on the board and don't want to just start tuning stuff.

I also assume the small trimpots you are refering to are the conventional flat trimers that need a screwdriver to turn. I saw those but it would be a real trick to put a screwdriver on them.

- Pete

As a follow up to this thread, here’s a picture of one of the driver boards. The trimmer for Offset is on the left and marked with an O. The trimmer for bias is on the right and marked with a B.

- Pete

As a follow up to this thread, here’s a picture of one of the driver boards. The trimmer for Offset is on the left and marked with an O. The trimmer for bias is on the right and marked with a B.

- Pete

Nice pic. As soon as I can get my hands on a voltmeter, I'll be setting up my 2285.

Interesting that the manual for the 2270 lists a few more service procedures than the one for the 2285.

I managed to adjust the offset easy enough but the manual says 5 mv for the bias and I can't get it to go below 10 mv. The test points are a little hard to access. Hope I have the right ones. A third hand would help also.
Would it be better to pull the board to make these adjustments or would that require unsoldering a lot of wires?

I managed to adjust the offset easy enough but the manual says 5 mv for the bias and I can't get it to go below 10 mv. The test points are a little hard to access. Hope I have the right ones. A third hand would help also.
Would it be better to pull the board to make these adjustments or would that require unsoldering a lot of wires?
Hey RocknRum,
Can't help you with that 3rd hand :scratch2: , but a tip: don't pull the board out. These adjustments are usually made with the receiver open, assembled, almost ready to ship. Did you make sure you had disconnected the speakers before taking your readings?
Also, what kind of multimeter and what range are you using to take this reading? What reading do you get if you short the leads?

I have a Micronta LCD benchtop digital mutimeter that I bought in 1990 on sale for 120$. Regular price was 170$. It was the best Rat Shack had for sale at the time and it works awesome with lots of functions. Even has setting and test lead for checking diodes and transistors.
Reads 0 mv with test leads shorted. I usually have it set on automatic range rather than manual. I used it to tune up my 2250B and set it to factory specs easily.
This meter takes 4 C batteries and it still has the original ones in it and they still provide lots of juice. These are no name batteries that are yellow with black lettering and are made in USA. Also they're alkaline. I wish I could find more of these batteries cuz I'd put them in everything I own.
Getting back to the 2270, the person who sold it to me said it distorts past half volumne. I didn't notice any big difference in sound but I don't think it sounds as good as my 2250B. The manual I downloaded off of the net seemed good but the schematic didn't seem to jibe with my driver board.
I read somewhere that Marantz had different schematics for some 2270s based upon certain groups of serial numbers. That would be confusing. Is there any truth to that?
I also noticed a couple of caps with some discolouration. It appears some of the component identification numbers on the pcb are wearing off also.
I'll probably have to do a ton of reading and ask a few questions before this baby is pumping good sound.

I have a Micronta LCD benchtop digital mutimeter ...
Reads 0 mv with test leads shorted. ...

Seems OK to me. Did you switch off the speakers before taking your reading?

...
Getting back to the 2270, the person who sold it to me said it distorts past half volumne.

Hmmm, you would need a properly setup electronics shop bench to test that. How did he know?

I didn't notice any big difference in sound but I don't think it sounds as good as my 2250B. The manual I downloaded off of the net seemed good but the schematic didn't seem to jibe with my driver board.
I read somewhere that Marantz had different schematics for some 2270s based upon certain groups of serial numbers. That would be confusing. Is there any truth to that?

You got me. I have no idea. I wouldn't be surprised to find slightly different components in a big series, but not different schematics altogether.

I also noticed a couple of caps with some discolouration.

They are saying: "Recap meeeeee". ;)
Check my Recapping HOWTO.

It appears some of the component identification numbers on the pcb are wearing off also.
I'll probably have to do a ton of reading and ask a few questions before this baby is pumping good sound.
For a more extensive overhaul I would suggest professional services.

Yes the speakers were unhooked and volume turned down all the way and selector set on aux with no input going to it. I let it warm up for at least 20 minutes.
I don't know how he knew it was distorting unless he measured it. I am going to have to spend some more time with this receiver before I come to any conclusions. Or questions. I'm in no hurry to get it going anyway. I'll just take my time. If I learn something it will be worth it.

To solve the "third hand" issue, get some test leads with mini grabers on the end. Then you can just clip them to the test points. Radio Shack has some mini grabers that slide on the ends of meter probes.

As far as not being able to set the bias, did you see EchoWars recomendations for using a different test point and value?

- Pete

Yes, thanks for the reminder. I planned on getting some small insulated roach clips. That way I don't send 45 volts to ground again from my test lead and yell the "F' word in front of a startled immature helper.
I assume your talking about EW's monstrous thread on DC offset. If so I'll have to read it again.

There is another thread on setting bias and offset on the 2270. In it EW has an alternate procedure. Do a search for 2270 bias and it should come up.

- Pete

Well, I couldn't find that thread. But anyway I did manage to check bias on both channels and with the trimmer turned all the way clockwise on the right channel it wouldn't go below 10 millivolts. Left channel 7 mv was the lowest I could get. The manual says it should be 5mv. I set the DC offset on both sides to around 2 or 3 millivolts. Then fired 'er up and listened to a complete cd. It didn't sound too bad, but didn't seem quite as powerful as my 2250B.
Being a 2270 it should be more powerful. Sound seemed equal though on both sides and no scratchiness with any of the controls and no sound dropouts.
I had to turn the volume up to 11 o'clock to get the same sound level that I would get from my 2250B at 10 o'clock. My ears didn't pick up any audible distortion, but it didn't seem to have the magic that the 2250B has.
I think aging components are a factor here.

http://audiokarma.org/forums/showthread.php?t=88544

Thanks, that clears up the confusion.

Using those bias test points, I get 22mv for the right channel and 20mv for the left. They both are around 10mv or so when the receiver is first turned on and slowly climb to these values and stabilize after half an hour. Also I have the trim pots turned all the way counter clockwise to get the values this low. I have the offset between 1 and 2 mv on both channels and the receiver sounds pretty clear. At least to my ears.
Will this somewhat high bias voltage burn out a transistor over time and what are the possible causes to look for in regards to the high reading? Anyone?

Something is not right if you can't adjust it to spec. I don't know enough about it to say for sure, but I would be concerned about possible damage to the output transistors. Fortunatly, if the bias is too high, the outputs will get hotter than normal. Keep an eye on the temperature. If they don't get too hot, and the sound quality is OK, then you may be OK.

- Pete