Fisher 800c project for 2014

Phono looks good Don.

C14 and 15 are shown as 18 pf on the schematics (all of them), and in the parts list. I'd go with that unless you already have 10pf in there. And really they probably won't affect SQ, or operation of the output section, by leaving the old ones in. I don't normally change out any ceramics on my FISHER's, except if it would be a coupling cap, and not directed to ground. FISHER used higher quality ceramics, and I really can't determine a difference in SQ between them and a good quality film, by ear (but then I'm 1/2 deaf too (according to SWMBO)).

Larry
 
I am going to ask Jim McShane about this discrepancy between 18pf and 10pf for C14 and C15. Normally he notes different values in the parts list. 10 and 18 are too similar visually

But I agree to leaving the existing 18pf caps in place for now.

That metalbone kit sure looks sophisticated with its fancy diagrams and whatnot
 
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Don; I GOOFED. Sorry for the oversight. Only the 63 Executive and the 20001-29999 version are 18pf. All other versions (64 Executive, 30001 and up, 30001-39999, and 30001-49999) show 10pf. With this being a '63 Executive and C14-C15 being in the output section (with the different output/PI Section, it's possible that this is a 63 Executive only part.) The 20001-29999 match the all the higher numbered as far as the actual circuit is concerned. It's possible that it is correct in the 20001-29999 and was changed for the 30001 and higher versions. OR that it's ONLY a 63 Executive part, and the 20001-29999 version ('63 standalones) was mismarked.

The Center Channel output is wired the same in the '63 Executive and the 20001-29999 version. It is different in the 30001 and higher, plus the 64 Executive.

So I think maybe we're getting into FISHER not keeping up with the manuals, like they mis-numbered in the 400.

Let's see what Dave thinks also.

EDIT: Thursday 15DEC14 1030am.

I p.m.ed Dave and he tends to think it's because of the different output transformers in the '63 Executive. Remember the '63 Executive uses the T990-116 output transformer and all other versions use the T991-116.

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Hi Larry -- The different value would not have anything to do so much with the phase inverter or the center channel output, as it would with the output transformers themselves. Didn't you say that the early version (i.e., the Executive version) of the 800C used a different OPT? If so, there's your answer. The different value follows the different transformers used.

Using one value for the other with either transformer will hardly make significant differences. It was part of Fisher's scheme in producing HF stability in the output section. It would be good to use the correct cap for the OPT at hand, but will hardly cause any problems if the wrong value is used.

I hope this helps!

Dave



Larry
 
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Okay, Thanks Larry, Dave
Jim McShane is out for the week till prolly after Christmas.

Interesting that some big transformer units use 18pf as well

So my options:
Just leave the existing 18pf? They both measure within range like 2%
Maybe replace with new 18pf?
Maybe replace with new kit provided 10pf?

BTW: Jim refers to my unit as The Executive 950 "Oddball"
 
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I would suggest again that because the effects are subtle, Fisher likely switched over the OPTs to the larger model, and switched out the 10 pF for 18pf as supplies of the cap flowed into the pipeline. That is, it was much more important to pair the correct chassis with transformer (so that the mounting holes would line up), than it was to absolutely get each transformer type and cap value correctly aligned during the change over to the new transformer. Almost surely, any large transformer unit using the smaller cap value was produced during the changeover to the updated model.

Dave
 
Personally I'd leave them be if they are only 2% out. But if you have new 18pf, why not. But I'd leave them as 18pf. Your's is one of the earliest built 800-C's out there(10189a, meaning the 189th 800-C built ), so I'd go with the 18pf. I'd be a little bit more on the fence if the serial was closer to 20000.

Larry
 
C21 and C22 replacements

I left the 18pf 10% caps in place (one measured 16.7 the other 17.8)

onto C21 and C22

Take a look at this picture of the existing C21 and C22 caps
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C21 and C22 are 330 ceramic caps as built.
The McShane kit has .001 for C21 and C22 replacements

And I cannot find that third ? 330 cap on the schematic

Is this maybe the same 1202 alarm as before, just move on with originals? Go for the landing

Do all these differences still add up to changing the 4 x .047 to .1 and the 330k resistors to 200k?

I was saving the PIO caps for last
 

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Again, these were OPT specific. Most of the latter 500C/800C units I've seen (all with the bigger OPT) in fact have a .001 value installed in that location by Fisher -- but I have yet to find any Service Manual that indicates that value in any of the units produced. Best to stick with the value that was installed in your unit. Such a change in value would NOT be subtle in your unit.

Dave
 
What about the .047 caps changed to .1 or the 330k resistors changed to 200k?

Are these still relevant changes?
 
Yeah. The 330pf are bypassed with the 3.9K's which makes them C21 & C22. Go with what Dave indicated above. FYI There are 3......count'em 3 more 330pf ceramics in the tuner section. C107, C108,C109. Just off of Z-7 (right of it) and between it and R152, R153.
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There's enough weird shit in the Executive to keep The Hair Club for Men in business a long time.

The .1uf and 330K to 200(or 220K whatever Jim sent) change is relevant to the Executive because of the output tube used. Doesn't matter if the tubes are old stock, NEW Stock, Russian, Domestic, etc. The grid return resistors are flat out too big a value for the 7591. So it has to be brought down. A good range for them is between 200K and 220K. Then you have a R/C network that has a timing constant. When one of the components is changed the constant also changes, so someone with a lot more Math knowledge than I do has to figure out the timing constant based on 200K to 220K resistance. .1uf is what most everyone has been using for the last 3-5 years now. According to a post that Dave made a couple years ago, the actual value of the cap is around .072 as I remember it. Closest to that is .068uf. Also .082uf. .1uf is acceptable as long as the unit doesn't have a tendency to oscillate with the .1uf installed. My two have been running with .1uf's for at least 2.5 years now and absolutely no problems. Plus it's a commonly produced value.

Go ahead and install the 2 330pf's @ C21 & C22 and don't worry about the 3rd (keep it for a spare). Change out the coupling caps and resistors, kick back and have some fun with it.
 

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R21 r22 r23 r24

Original as built
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The 330k resistors R21,22,23,24 are changed for 200k resistors
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The .047 caps are changed to .1 PIO caps
 

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Completed install

Here is the completed kit install
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Questions?

What about these caps?
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Powering up after the restore

How would I go about powering up the unit after the restore?

What voltages should I measure?

The parts I replaced:
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Inspection gig

Found some debris after the restore. A can of air and careful inspection saved the day
 

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Here is the completed kit install
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Questions?

What about these caps?
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Looks good Don. She should come right up without any problems.

The single "?" cap is the C210 (IIRC) that is 1uf/350V. It's for the MPX and will cause fuzzy, distorted sound when it goes. You can change it out with a 1uf/400V film cap (non-polar) and not have to worry about it ever again.

The dual "?" are part of the matrix circuit (I haven't got the unit open so I'm going from Memory here). should be a 2uf 50v or there about's. and a .5uf I think. Change both out. I think they are C65 and C67. I'd have to back track them with the unit out. (go ahead and change them out anyway if you have them. If not, change them out soon)

I can't remember what the .047 is for, but IIRC it's part of the signal path, even tho it's right in the middle of the tuner area. .047/400 is fine.

Use a 150W bulb at minimum on a DBT. As you have all new caps in it, you won't need to reform anything. If it "flashes" bright and then goes dim you'll be fine. Wait a minute or two and look for smoke. If no smoke (there shouldn't be any and it plays decently), go ahead and put it on the wall.

Voltages to check on variac @ 117VAC;
OUTPUT TUBES
Pins 3,4,5,6

Heaters on V3,4,5,6,7,8,9,10. All should be between 5.8 and 6.2v. NO HIGHER than 6.3.

Voltages can be + or - up to 10-15% with a wall voltage of 117vac. This is due to component variations from nominal value.

The voltages on the output tubes at pins3, 5, 6 will tell how well the tubes are biased, and whether they are balanced or not.
 
Speakers are connected


FIRST POWER UP:

The 150 watt bulb did not dim down very much on power up so I shut it down
I powered it up for about 5 seconds

It did dim but it did not dim down like all the way

I have a variac at 117vac and a 150 watt dim bulb and a amp meter

The amp meter drew the same .8 amp as during the initial cap reform
 
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Okay I just cinched up my drawers and let er rip with my hand hoovering over the off switch
The bulb did dim more after a few seconds

The unit came up and played music out each channel through the aux port

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sounds fine... sounds real fine

I removed the dim bulb but kept the variac and amp meter

It is drawing 1.5 amps now

Voltages measured after warm up

V14
Pin 3 = 425
Pin 4 = 379
Pin 5 = 339
Pin 6 = -16.81

V13
Pin 3 = 426
Pin 4 = 373
Pin 5 = 355
Pin 6 = -16.79


V11
Pin 3 = 424
Pin 4 = 381
Pin 5 = 359
Pin 6 = -16.85

V10
Pin 3 = 425
Pin 4 = 381
Pin 5 = 382
Pin 6 = -16.85

I have let it play for an hour now, listening to the CD soundtrack from Blade runner. Tuner works okay but could benefit of an alignment


I want to test the phono section
I'll hook it up to the Wharfedales next
 

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WAY TO GO, DON!

Hopefully the Pin5 measurements are mv. If so, it looks good. I'd keep a close eye on the output tubes. Nice fairly tight spread of ma between high and low. 5ma with used tubes and running stock bias voltages isn't too bad at all. Could be better with an IBAM or Dave's Balance/bias board. Without the IBAM or BAL/BIAS boards this is as good as it gets with the tubes. And they are in the recommended range for operation today, albeit on the high side. I like bias voltages of -18v to -20v with tubes drawing 33 to 36ma. Obviously these aren't gonna do that, but they are close.

I'd leave them as is in the current positions with the stock setup. If you DO want to setup a bias adjustment, go with Dave's BAL/BIAS Board. It's a good setup and I'm liking it more than the IBAM if nothing more than ease of adjustment.


percentages are approx. and based on MAX disspiation of 19W. I rounded up if within .2%.
V10...14.4075w 76%
V11...15.123w 79.6%
V13...15.2216w 80%
V14...16.235w 84%

You DID GOOD! You can do the BAL/BIAS board later. But for now, kick back and have a mug of your favorite beverage! You earned it.

Larry
 
Yes, I wondered what that mV was

Well I could do the SERVICE NOTIFICATION that dave put out
I read about the IBAM mod and I think I could pull it off since it is such a great thread

but for now...

FISHER 800c PROJECT FOR 2014 IS COMPLETE
 
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