Audio Transformer Diplomat D-39/Chassis T-290

[gadget73]

more or less. I don't remember if I ever measured the output power of mine but 8 watts is probably about right. With efficient speakers thats actually enough. Don't feel too bad though, they cheated me on my TA-600 as well. Fisher claims 40 watts, it does 18 per channel or 9 per channel with both driven.

yeah I never made any follow ups. Got too involved in rebuilding it and just never turned the camera on. It takes a lot longer to do things on video than it does to just do them.

usually its just bad grease. The parts get sticky and none of it moves properly. Cleaning it out and replacing with fresh does the trick most of the time. Alcohol or mineral spirits will get the old crap off. I use silicone grease, white lithium is also fine. Basically any relatively light grease that won't melt out or get stiff is what you need. The motor and platter bearing want some sewing machine oil or something similar to that. The trip mechanism under the platter just has to be clean and dry, same with the inside of the platter, the motor spindle, and the idler wheel surface. A wipe with rubbing alcohol will take care of it. If you grab a service manual for the AT6 or AT60 it will show you which parts should have what.

 

[rufleruf]

Just got home with a new carload of Tube gear, but I digress...

The one I have is a 290-T, so perfect fit for parts I would guess.

Gadget73 - I have a ZZ50210-9 for you - and a box of tubes showed up yesterday that once empty will be the perfect size to mail it to you.

 

[gadget73]

awesome, I'd appreciate that very much. Wideband TA-600 here we come, once I really get the hang of using my alignment generator I'm messing with mono tuners I don't care about first before moving on to my better stuff.

 

[larryderouin]

Jim; The 290-T as used in the Diplomat and the philharmonic are the same unit. Fisher used the same chassis in adjacent models up and down the product line. As long as a chassis is marked 290-T (it's not T-290 as the model number comes 1st then the "T" for tuner or "A" for Amplifier, however the 290-T being a receiver should have been 290-"R" in the greater scheme of things) the parts are interchangeable.

Larry

 

[Jim 2018]

more or less. I don't remember if I ever measured the output power of mine but 8 watts is probably about right. With efficient speakers thats actually enough. Don't feel too bad though, they cheated me on my TA-600 as well. Fisher claims 40 watts, it does 18 per channel or 9 per channel with both driven.

yeah I never made any follow ups. Got too involved in rebuilding it and just never turned the camera on. It takes a lot longer to do things on video than it does to just do them.

usually its just bad grease. The parts get sticky and none of it moves properly. Cleaning it out and replacing with fresh does the trick most of the time. Alcohol or mineral spirits will get the old crap off. I use silicone grease, white lithium is also fine. Basically any relatively light grease that won't melt out or get stiff is what you need. The motor and platter bearing want some sewing machine oil or something similar to that. The trip mechanism under the platter just has to be clean and dry, same with the inside of the platter, the motor spindle, and the idler wheel surface. A wipe with rubbing alcohol will take care of it. If you grab a service manual for the AT6 or AT60 it will show you which parts should have what.

First of all, wow, really greasing up an old AT6 did the trick. All functions now work EXCEPT the selector arm does not return at the end of a record. Mind you, it will correctly move to release multiple records. So when removing an album off the turntable, I have to awkwardly use my finger to push it back. Not the end of the world but if there's an easy fix or something to look at, let me know. Other than that, the whole thing works. FYI, this AT6 was made 35 week of 1963.

 

[gadget73]

the little finger, or the over-arm? The over-arm should just drop straight down until it bottoms out, the little finger drives off the mechanism in there somehow that I can't recall without looking at it. Possibly also still a lube issue though, I don't remember having problems with that. Garrards are pretty tough, but the lube hasn't aged well. Its almost all metal though so there isn't much to actually wear out.

If you mean the center spindle, it will stay out at the end of the stack. Just pull the spindle out and take the records off the platter. It pops right out of there.

 

[Jim 2018]

the little finger, or the over-arm? The over-arm should just drop straight down until it bottoms out, the little finger drives off the mechanism in there somehow that I can't recall without looking at it. Possibly also still a lube issue though, I don't remember having problems with that. Garrards are pretty tough, but the lube hasn't aged well. Its almost all metal though so there isn't much to actually wear out.

If you mean the center spindle, it will stay out at the end of the stack. Just pull the spindle out and take the records off the platter. It pops right out of there.

The little finger thingy...the manual says it's the "Selector Arm" (just to the left of the "Record Overarm") and is what moves to automatically drop a record onto the platter or the next record in a stack of records (in conjunction of course with the center spindle also releasing in tandem at the same time as the Selector Arm moves out of the way).

What I don't get about it is that it is smart enough (and able enough) to correctly move out of the way in order to drop the record onto the platter or if playing multiple records to move only to just drop one record but it doesn't get itself out of the way when the record is over. I played records on it for a few hours after my last post and I am wondering now if it isn't "behavior by design". The amount of movement required to drop the record is less than it would be to move out of the way when removing the record from the platter because the record's weight will partially push it away (some). Whereas it needs to be farther way to remove and since one's hand is down there anyway, maybe they decided it wasn't necessary to articulate that arm to the extreme for record removal. Not sure, just a theory.

Otherwise everything else works exactly as expected. I can't agree more with the suggestion that everything needs to be lubed. The mechanism is like a fine clock and if one part sticks it effects the downstream mechanical behavior of the whole turntable.

And if that rubber wheel survives or could be replaced if need be, those AT6 turntables will never wear out. Once I get my tube order tomorrow (missing AM radio tubes, go figure) and a long term fix for the borderline right channel audio output transformer, this Diplomat D-39 is back in business! Not sure about the power switch on the volume knob, might just put a toggle switch on the back somewhere and call it a day.

 

[audmod01]

I remember the IHF Music Power rating and the power wars the manufacturers engaged in. It was strictly a sales gimmick and most honest high fidelity publications decried the situation but to little effect. Those of us who knew what the circuits were truly capable of always told customers the real truth when we could. The legitimate rating was true root-mean-square power over the rated frequency response at a specified harmonic distortion level. Anything else was smoke and mirrors. The situation became so bad that eventually the government stepped in and the dust began to settle. Unfortunately many manufacturers were caught up in the competition for sales and if they did not advertise in a similar manner to that of the other companies they lost sales. The rest is history.

The tube manuals are the source of the 8.5 watt power level the tube can produce. With two power pentodes in one envelope there is not only a current limit per tube section, but a heat dissipation limit. Dave worked wonders with his EFB on other circuits, but for these I think as long as a person is satisfied with the performance of the unit I would leave well enough alone. If the ELL80 tubes eventually become unavailable, then it might be time to change to the EL95 tubes. Then there is the issue as to whether the power supply section can support the EL95 tubes.

Joe

 

[gadget73]

ok, that thing. Yeah that parks sticking out over the records normally. It has to do with the sizing mechanism so the arm drops in the right place. Basically its the 12, 10, or 7 inch detector. 12 and 10 hit in different places, 7 doesn't touch at all so if that happens it assumes that size. It doesn't actually have anything to do with dropping the records, that happens with a very small little finger in the middle of the stacking spindle.

Just pull the record spindle out and then you can pick records up towards the front so it doesn't get in the way.

Also a little tidbit on the tube power ratings in the manual, thats plate to plate power. It does not include losses inside the transformer. Those run somewhere in the 82% efficient range, so honest power at the speakers is probably 80-85% what the datasheet says it will be.

some reading on power measurement systems.
http://soundandsong.com/Issue004/004_PowerAmpRatings.html

"An FTC rating requires that the amp undergo a "warm-up" test, meaning the amp’s output ratings are measured after 60 minutes at 1/3 power and five minutes at full-rated power."

basically if it survives that, it'll work in your house just fine. Nobody runs their amp at maximum power output across the whole band for 5 solid minutes.

 

[Jim 2018]

I remember the IHF Music Power rating and the power wars the manufacturers engaged in. It was strictly a sales gimmick and most honest high fidelity publications decried the situation but to little effect. Those of us who knew what the circuits were truly capable of always told customers the real truth when we could. The legitimate rating was true root-mean-square power over the rated frequency response at a specified harmonic distortion level. Anything else was smoke and mirrors. The situation became so bad that eventually the government stepped in and the dust began to settle. Unfortunately many manufacturers were caught up in the competition for sales and if they did not advertise in a similar manner to that of the other companies they lost sales. The rest is history.

The tube manuals are the source of the 8.5 watt power level the tube can produce. With two power pentodes in one envelope there is not only a current limit per tube section, but a heat dissipation limit. Dave worked wonders with his EFB on other circuits, but for these I think as long as a person is satisfied with the performance of the unit I would leave well enough alone. If the ELL80 tubes eventually become unavailable, then it might be time to change to the EL95 tubes. Then there is the issue as to whether the power supply section can support the EL95 tubes.

Joe

So a question. I sort of remember like 25 years ago when I was in college and more into stereo equipment that higher end solid state amplifiers would pitch being "high current" such that a lower wattage amp with "high current" could drive the speakers/woofer better. To the extent I'm conveying this concept correctly and to the extent that this isn't more marketing mumbo jumbo, are tube amps "high current" and superior in sound output to a cheap "low current" solid state amp of the same wattage? Anecdotally, to my ears the amount of clear sound this Fisher can produce on ELL80 tubes "sounds" more than 8.5 watts a channel and am wondering if "current" is the reason for the illusion.

 

[larryderouin]

Tube gear is Hi Voltage-Low Current , while Solid State tends to Low Voltage (<100V rail voltage) and High current. Watt's is Watt's in Ohms law, no matter how you figure the Math. Speaker efficiency plays a big part in the perception that tube gear sound more powerful at a given wattage rating. Tube gear usually is paired with higher efficiency speakers, while Solid State stuff can play low efficiency speakers fairly well. I think you'll find if you set up a mic @ 1 meter from the cone center on the console, and toss it a 1watt signal, say @ 1kHz you can figure the math to get speaker efficiency. It should be in the mid 90's or even high 90's.

Take a 20W solid state receiver and pair it with a couple of different known published efficiency speakers. Leave the volume setting at say about 9:00. Set one pair on spkr "A" and the other pair on spkr "B". One pair rated for about 86-87db and the other about 96-97db. Notice the difference in SPL with the same volume level? Now take the higher efficiency speakers and plug them into the 8W console and you can approximate SPL's with that combo that the 20W Solid State with the Lower efficiency spkrs do at just below clipping. And that's basically how an 8W console can approach the SPL's a 20W Solid State receiver or amp does.

 

[Jim 2018]

I noticed that speakers in the console are louder though I've experimented with newer speakers connected to the chassis and while not quite as loud, all other things being equal, they still deliver a full sound for 8.5 watts a channel (minus any audio output transformer loss).

 

[Jim 2018]

Please note, the understanding I have is that the primary winding of your defective transformer is intermittently going open. When/if it does go open, continued operation under that condition is very hard on the output tube the defective transformer operates with as the screen grid element in the tube affected must then absorb all the current flow, which it is not designed to do. As a result, the screen grid within the tube can be destroyed rather quickly when the tube is operated under that condition. It would be best to not operate the unit until a proper replacement transformer can be installed.

Dave

Well, I think it's more of a partial short...I think...the volume goes way way down and becomes distorted. I've since employed a decent work around by tightening a wire tie around the transformer. I noticed if I squeezed the transformer with my fingers near the bottom, it would cooperate. I've run the system for several hours or more since and not a lick of trouble. No static, no drop outs, as clean as the other channel.
Though I'll keep your post in mind if it starts to exhibit symptoms again.