A few questions about M-85 operation...No class A change and not impressive o...

Hi, Avionic,
When i received the amp the boys at FedEx did a wonderful job of making sure that they broke the "C" speaker + post and caved in the left side cover that you remove to mount the rack handles. I repaired those cheezy posts and everything is well once again That was the only damage I saw. ALL 3 sets of speakers sound the same. The relays work fine as well. When I first power it up the protection LED is on for about 5 seconds and then it "clicks" and all is well as normal.

BTW, Norman at Analog Alley said to tell you "Thanks" for the referral :)
Sorry to hear about the problems with the amp. How well was it packed? Did the seller pack it or FedEx?
 
Sorry to hear about the problems with the amp. How well was it packed? Did the seller pack it or FedEx?


Seller packed it although not nearly as well as I would have but it was decent enough. I started probing around and this one luckily is not plagued with the DSBG blues. Very little surprisingly and not one component corroded.


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It was supposed to work. The guy even sent me a video of it in action prior to when he shipped it to me and it was working. I trust the seller and he is doing the legwork to get the claim settled for the damaged goods. I figured I would hang on to it as it now surely is a "fixer upper" sadly. I intended to re-cap the thing and check it all out so I guess I will have to do some extra work. Who's to say if I was to send it back and get my money back that the next one I find will turn out to be a lemon as well.

Now then, moving along...I started checking the power and what I have found, right off the bat, is the voltage from the power supply is weak on one rail.
The schematic shows 88.1(-88.1) on the H rail which is exactly what I have. However, on the L rail the schematic calls for 49v and I am getting 35.6v.
bequsada.jpg
 
Now to further, the secondary taps from the xfrmr are as such:
Y=28.3 Vac
O=28.3 Vac
R=66.2 Vac
BL=66.2Vac

What would cause the discrepancy in the voltage? I am not sure but if the schematic is calling for 49V and I am producing 25% less I suppose this would create a problem, yes?
pyburuze.jpg
 
I just purchased a very good copy that I can actually read. Now I will try to bonehead through. More than likely, however, I will probably just end up sending it back for a refund. I have enough projects and this Yamaha is just a boat anchor as currently is. I'll mess with it for a little while but I don't know. All I can say is all of the functions, aside from the auto A switching circuit are in working order. But when there is barely enough volume coming out with a good input going in something is out of whack. The LED meters might be saying I have 200 Watts coming out but my ears say otherwise. 7.4V out at the speaker terminals is not 200W of power!




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When things calm down, take the schematic and manual to a Fed-X center where they have the huge scanners and Post for those coming after you. Watch that they don't give you a 100mb file as the scan on the schematics, maybe the text vs photo setting and or color vs BW
 
I think there is a problem with the values shown in the schematic
scratch2.gif


Do both channels measure the same?

These are some measurements of my M80 and bmanone's amp, and LB is always lower than expected:
BLACK-BLUE: 66.5VAC
BLACK-YELLOW: 30.5VAC

bmanone:
HB = 89.7v
LP = 50.58v
LB = 39.5v

My amplifier:
HB = 92.7
LP = 50.5
LB = 41.7

Service Manual:
HB = 88
LP = 49
LB = 48
 
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Well, I just packed it up and dropped it in the local repair shops lap. Gonna move on to other things. I'll report back when I find out what he found.

..Bud
 
I think there is a problem with the values shown in the schematic
scratch2.gif


Do both channels measure the same?

These are some measurements of my M80 and bmanone's amp, and LB is always lower than expected:

BLACK-BLUE: 66.5VAC
BLACK-YELLOW: 30.5VAC

bmanone:
HB = 89.7v
LP = 50.58v
LB = 39.5v

My amplifier:
HB = 92.7
LP = 50.5
LB = 41.7

Service Manual:
HB = 88
LP = 49
LB = 48​

Both channels measured identically.
I even pulled the mains from the PS boards and measured the voltages without anything connected and they were just a couple of volts higher. There is either a discrepancy in the SM or we have the same situation yet, yours works correctly.
Thanx for the help!
Bud
 
Hi, Avionic,
When i received the amp the boys at FedEx did a wonderful job of making sure that they broke the "C" speaker + post and caved in the left side cover that you remove to mount the rack handles. I repaired those cheezy posts and everything is well once again That was the only damage I saw. ALL 3 sets of speakers sound the same. The relays work fine as well. When I first power it up the protection LED is on for about 5 seconds and then it "clicks" and all is well as normal.

BTW, Norman at Analog Alley said to tell you "Thanks" for the referral :)

I'll bet. It ends up being a cracked solder connection on either the main or the filter PC board. Or even one of the PC boards is cracked.:scratch2:
 
I think It's strange that the meters measure the correct amount of power, they take the signal from the power outputs. Seems to be a problem between the output transistors and the binding posts...
 
I was kind of bewildered myself. I just threw in the towel and dropped it off at the local tech repair shop. I've had them do
repairs in the past on vintage gear and they are really good. They will give me the low-down once it is done probably next week. I guess I was just a bit peeved because of the whole shipping fiasco. I figured I'd let someone else fix it since I had the funds to do it this time. I am still gonna find out what it was and I will post a detailed summary.
Thanx!



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