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I did deoxit all the switches (see my post #11). Oh, and the inputs each have their own pushbutton. I just don't know - I've had some crazy intermittent problems with other electrical devices in the past, including cars and they are sometimes pretty hard to figure out, guess that's why the...

OK, dammit the amp makes a liar out of me. I switched the speaker cables back over to "A" to that tape and CD both sound OK while phono does not and when I try phono again, it comes through sounding fine! Let's put any further troubleshooting to the side while this amp decides what it wants to...

Thank you, goat67 for chiming in. The answers to your questions are: yes, left and right channels on speakers "A" are really distorted, especially when bass freqs kick in. Only phono appears to be affected. I do not have the education to make a schematic from looking at the board, wish I did.

Just found the problem. I deoxit'd all the switches and put the unit back in the system. No change, both channels sound like they are being driven into clipping at low volumes. I then changed the speaker cables over to channel "B" on the amp. Lo and behold the good sounds are back. This amp is...

Amp still sounds great with cassette, reel to reel and CD. It is only the phono that sounds bad. I've been an electronics assembler and solder tech for many years and it does not look like the transistor in question has ever been swapped out, so I would say that it's original. The MPS9633 you...

would any other pictures help? I am woefully short on any other info about this amp - it is a beefy little sucker due to having a massive low profile square transformer inside - it's approx. 11x17x3 inches high but weighs like a bowling ball. :D

I wish I could find a schematic, but as I said I can't even find specs for this amp. The transistor has the Motorola "M" then next to that is a "C" and below those 2 is "9633". It also has stripes on the backside. Here are some pictures of the thing...

My extremely clean Yashica Electro 35 GSN with close focus attachment...

I am working on a Sherwood integrated amp model AD-400B phono preamp section. The caps look OK, I am suspecting the transistors. It was playing great for a few days, then all of a sudden I start hearing a reduced output that is very fuzzy sounding. I have tried 3 different turntables and get the...

Here's the link for the interested - http://portland.craigslist.org/wsc/ele/1799587094.html

Someone (no, not myself or anyone I know) just posted on the Portland, Oregon Craig's List a pair of these...he (or she) says "In pristine condition, stored in air conditioned storage & plastic wrapped all of these years, unbelievably clean". Judging by the gigantic pics they posted they are...

Gentlemen, I believe the amp is ready to fly...my readings are 2.5 to 3.0 millivolts between pins 3 on both sets, and the voltages are -19.60 & -19.70 on one pair and -20.18 & -19.12 on the other pair. Thank you both very much for the assistance! - Kerry

I appreciate the generous clarifications, Craig - I'll give it a try... If the negative voltages on pin 6 of each pair of tubes is way off, would I want to leave the balance pot as near to zero millivolts btween the number 3 pins of each pair and run it that way til I get new tubes or go back...

Thanks Ryan, I know about the long hours - I do about 11 hrs a night starting at 5 PM.... I think I can say that I've got it whipped, I switched to a 10 ohm Mills resistor and the meter says the tubes are pulling 34 - 35 mA each and the grid voltage is between -19 and -20 volts. Woo-Hoo...

Thanks, NOS Valves - I appreciate the help, and I'll try to refrain from using the amp as a home therapy kit...LOL - Kerry

Thanks for clearing that up, Craig...jeez, now I think I will go stick my tongue on the center-taps......

OK, the voltage to pin 6 runs from -18.40 to -19.44 measured with the black com probe connected to chassis ground and the red positive probe connected to pin 6 of the 7591's. I looked at the wiring of the silicon bridge rectifier (Radioshack) and the positive terminal is connected to a black...

A-HA! - (maybe...) the cathode resistors, when measured (in-circuit) are 198-208 kohms. According to the schematic, and the color coding - orange,orange,yellow,silver - they should all be matched and read 330 kohms...looks like another trip to the parts bin...any advice on what wattage...

Hi Ryan - I made up a little chart (hope it's readable)of the measurements I've been seeing from the effects of changing out dropping resistors in my quest to get a 35 mA current draw out of these output tubes...looks like something is screwy with the channel that has tubes 1 & 2...what do...

So, going lower in resistance on the dropping resistor won't potentially harm anything in the circuit ? Reason I'm asking is, I'll go ahead and order a Mills wirewound because the "16 ohm resistor" I've got in there consists of two HUGE, UGLY non-inductive 8 ohm power resistors soldered...

Ryan - I tested our ac line voltage - it is 121.1 v (if that has anything to do with it)...I know the Scott is rated for 117 v.

Yep - looks like I've got the center-taps located, but attaching positive probe to that and the negative probe to ground yields 455 volts! Yowza! the 16 ohm dropping resistor is allowing me to measure a current draw of 35.5 - 36.5 mA between the center-tap and pin 3 of every output tube...

Ryan - I think I'd better double-check with you to make certain I am measuring this correctly... Is the 'center-tap' a red wire that comes out of one output trans and ties to the other output trans, then goes over to the two tall, white, "tower"-shaped resistors and then through one of the...

Ryan - Wouldn't it be 96 mA that my output tubes are pulling (48 mA + 48 mA = 96 mA)...? Is that right ? - Kerry

Hi Ryan, Well, I went down to the nearest radioshack and got a $19.95 meter and I measured the current draw...it is reading about 48 - 51 mA on each plate - I went ahead and used the pots to balance the pairs. I've been playing it for hours, it sounds pretty good. I'm in the dark about the...