Stupid questions about fisher 80AZ

Any cathode feedback would have to be wound within the transformer.

The feedback is set up to introduce an opposite-polarity signal into the mix to help flatten out frequency response. There are a number of ways to get it done, the more economical method is a simple resistor off the speaker terminals fed back into an earlier stage of the amp. The cathode feedback winding is an extra cost, though it can work better if the transformer is made properly.

I think for this one, you'd need that specific output transformer to get it duplicated exactly. Maybe someone can wind you one, but there is a more than fair chance you'd have to sacrifice the one you have as a pattern for cloning.
 
simple resistor off the speaker terminals fed back into an earlier stage of the amp

Oh, I remember wondering why resistors were on the opt's of my first tube pulls, Silvertones I had.

Thanks Sir, for your succinct response! I am out of my depth and my rant was a legitimate question in my limited knowledge base. You make me wish I knew where to get quality training in this field.

There are a couple of leads I haven't exhausted. Not having the same cage controls or model number are becoming less important as I realize the scarcity and price of Fisher mono's.

I am thinking about fabricating a walnut base to hold the pair. The wires can all be routed out the back and preamp can rest beneath if not built into the base with few controls in the front. Trying to keep it stock - (well as close as I can now that it's all torn apart) and the idea of using external connections to reduce handling and wear seem like good benefits.

I don't think I will sacrifice the opt to get something made that I prob can't afford to buy, what would be the ballpark for a custom reproduction opt do you think?
 
Most of the wiring is replaced, Still need the RCA and volume pot but havent decided weather to use a new bourns or try the old one. Cleaned the old ones with deoxit and they all seem smooth now.

On the soldering and the stuff in pics I will explain and welcome pointers.

Pic 1 just close up of joints
pic 2 overview
pic 3 single joint
pic 4 and 5 the small file I use to clean/expose metal on the terminals

I try to adhere to some of the pointers I have been given so I keep the following in mind-my rules for soldering.

1. Bare metal bonds a lot better so expose some that has not been exposed to the atmosphere right before soldering. This means a few passes of 400 grit sandpaper on the tinned leads and maybe the same or file on the terminal.

2. The solder joint is NEVER the mechanical connection. So I usually wind the lead long around terminals for redundancy-sucks when you have to unwind though.

3. Solder flows toward the heat so heat from the bottom when possible and fill in the voids.

4. Electronics don't like a lot of heat so use heat sinks when possible to spare the components.

So the old resistors were all left in place and not reworked, I have time to test them before the other parts get here so just gonna make a checklist and go through them all.

For now I just re-flowed all of the joints with 7% silver solder and went on. As it stands now all I need is the new magical Russian caps and the input segment then I will be ready to put it all back into the chassis and see how different the layout is compared to original. I will duplicate as close as possible from pics and attach the transformers. Once the wiring is acceptable I will rivet the sockets back into place with stainless pull rivets unless something else proves necessary.

The newly painted pieces have been on constant heat 90 deg f for 2 days and will be there through the weekend.

On the caps I plan to increased the 40mf 450v and 500v cans all to 50mfd 500v. The 50 mfd 150v pio to 68mfd 160v. I ordered .022 and .047 for the others but also .033 and .068, all in 630v. The other ceramic disc and radio caps all at same values but havent found a replacement for the 500pf 1500v yet.

Any comments guidance welcome...
More pics on progress to come after the weekend.
 

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I am out of my depth and my rant was a legitimate question in my limited knowledge base. You make me wish I knew where to get quality training in this field.

The majority of what I know about this stuff has come from hanging out here and reading a lot, usually to find out why the smoke came out of something. I have not a lick of formal training in the tube realm. Some of the concepts still apply to solid state gear, but I have very limited formal learning in that realm either. Most of what I know about that actually sort of derives from what I've learned about tubes over the years. Most of that stuff still confuses me though.
 
Most of that stuff still confuses me

That's even cooler then.

It's awesome though that so many people are proficient at this work and willingly share and guide less knowledgable folk through what would be otherwise impossible or at least very ardurous work. I know very little but seem to get by with a lot of help from peeps on AK.

What is nice also is that when I write something fairly broad or uninformed you or others answer the question anyway. So thanks again for making the enviornment conducive to learning, it is appreciated!
 
You have to consider also that a goodly portion of the guys in the TUBE FORUM and FISHER Forums are in their late 50's, 60's and 70's and literally grew up with them. I have no formal training either, other than that what I picked up as a kid going on TV Service calls with my Dad (when he was home between Submarine Patrols) and when I was a Teen, sometimes a friends mom would ask If I could look at the TV. Take off the back after I look at the problem, ID the section of the circuit with a flaky tube (x-ing fingers) and take tubes down to local drug store and test them, replace the bad tube. Occasionally I would get lucky and actually fix it and it would stay fixed. I stopped when I got married in the mid 70's. I started back up when I retired on disability and needed something to do. I gravitated to tubes and FISHER's mainly as I understood them. I'm still after about 10 years what I would call a "parts changer" rather than a "troubleshooter.". But everyone here is learning, even gadget and me. The HARDEST THING to learn is PATIENCE. Go slow, double check BEFORE going on to the next section, Rushing will hurt you physically either thru cuts, or burns, or at Worst, you on the deck after learning how to be part of an Automated Emergency DEFIBRILLATOR! And it doesn't do the gear any good either.
 
I'm one of the weirdos in that regard. I'm 35, tubes were dead and gone before I was even born. I was fooling with antique radios before I got my first computer in the late 1990s, having seen them as fairly useless until I found their value as a teenager. I'll let you figure out what I mean by that.
 
parts changer" rather than a "troubleshooter.

Yes this is the reality of our culture-we replace anything questionable, but then if we weren't replacing internal components on gear we would be replacing the gear and there is nothing made currently that can compete, that is unless you are financially well endowed...

I am huge into made by hand in America, I have worked a lot of manufacturing and kids these days let me tell you! The late 50's and 1960's were the time man. Things were built to be better, to go faster, to last longer, fly higher, sound better. Then the Japanese did pretty good for a while but they sold their honor out just like American companies did.

I owned a sansui amp in college and sold it when I moved out of my apartment-never could find anything that could touch that old au-717, until I started getting back into audio, I currently have 4 of them and they run the low end along with tube kits I have built taking care of mids and highs. Now the tube sickness is on me, can't shake it so I am just going to embrace it and get the best stuff I can. The fact that it will need repair at some point and maybe a tube now and then makes it a double bonus to learn to do my own work.

cheers
 
I stumbled into tubes because I found the circuits forgiving of an amateur's mistakes. Replace the smoked component and go back and find the cause.
 
Poet, love your rebuild. I have a pair of 80AZs I recently picked up (sorry, no extras), and your cosmetic refurbishment will be my template. Mine have started out nicer than your starting point, but I'll be hard pressed to have mine look better than yours when they are done. I can't wait to see your final results.
 
forgiving of an amateur's mistakes

I have not been super adventurous when it comes to that, been sticking mainly to George Andersons tubelab kits and I think they have kept me out of trouble.

I hacked up my first attempt at point to point refurb of some pull amps I had, actually bought the pcb kits to hide under the chassis of those but turns out you can build chassis around a board to look killer.

The fisher in this thread is much more widely illustrated than those first pulls and I have about 2 years more experience now with kits and soldering and component selection, but I know it's only a matter of time before something goes pop.
 
Mine have started out nicer than your starting point

Cool man! in that case if the paint is basically intact I would mask the non painted parts and lightly sand with 400 or 800 or just clean very well and apply by hand some min-wax matte polyurethane. The color will be original and the finish will look brand new. you can plastic polish it after that if it ever needs it.

I wish I had started with better but also glad I didn't.

I found some terminals that were perfect replacement and will post the updated hardware and other parts and sources before the end, just in case anyone is looking.

One clear advantage to this frame off resto is that the soldering on the bottom side of the phenolic plate mounted terminals was easy access.

should have some more shortly.
 
Well, I put the wire harness back into the chassis for fitment. Oh what a dad gum mess. Some of the problems are:

beginning at the front of the chassis

1. The RCA jack threads are too shallow to grab the nut-that is the grip length is too short to use in the stock configuration. The one inside Teflon washer only wont allow the nut to grab the threads, let alone the outside Teflon insulating washer. So I will end up swapping for another jack or sanding down the Teflon washers.

2. The hole for the new RCA jack was too small so I took it out 3 steps with a unibit-lot of good that did me-maybe check the fit-up of the piece better before this point next time. It's already soldered now mainly because I wanted to have as many loose wires identified and resolved before this point so maybe chalk this up to inexperience and under confidence.

3. The wires that I left too long are all too long. At the trouble of trimming them back I will end up re soldering them to more closely emulate the original layout. I think it will be a hum monster if I don't and I was cautioned about this and the tight quarters of the model before I started so I expected this but it still must be dealt with...

now at the back

4. just long leads coming off the air cooled resistor array and lot of slack to be taken out.

I used #30 cleco clamps to temporarily secure the sockets and the impedance switch if you are wondering what those are, and the pots are just slightly snug. Small bolts will work too but that is a lot of screwing around.

On the impedance switch I searched for 4 pole 3 position for a long time. Stack-pole calls it a "slide switch, 3 pos low-off-high 6a 125v" PN: S2013U Servalite brand at ACE hardware.

I got in some Russian PIO .022 K40Y from a guitar outfit in Colorado-they were fast but I paid too much. The K42 series is just as good in my opinion and I have a couple hundred on order but the shipping is slow. I covered them in shrink wrap because the leads are able to touch the outer case.

The other MAJOR problem at this point is the phenolic plate has the leads bent slightly up or down or outboard and it is sitting tall which both pose a risk of contacting the bottom plate chassis if assembled now-so that would be super bad and pose a possible high voltage hazard and probabally destroy the amp if I didn't fix it first...

This joker has a long way to go...
 

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I am asking this because I am coming to grips with the possibility of not finding a suitable mate for this good looking bachelor.

Fisher made more than yours, you just have to start digging if you really want another one. Besides, you are halfway there. The 80AZ is actually one of more produced mono amps they made. If yours has 4-ohm taps, even more so although it probably doesn't seem like it. I think only the 30A might be more common. One is out there for you, patience is always rewarded.
 
One is out there for you, patience is always rewarded.

Yes I am scouring the resources I have keeping both eyes peeled. I need a 55A also but honestly I will snatch up any fisher that is remotely interesting...or similar in output power to either of these as funds allow.
 
Found these terminal replacements on ebay. They are exact perfect fit new old stock.
Kulka 4 Pole Position Feed Thru Terminal Block,600 SERIES 3/8" SPACING
 
I put binding posts on my ugly 70As. Easier to deal with than screw terminals. They even look sort of period correct, they were harvested from some old tube-based test equipment.
 
I put binding posts on my ugly 70As. Easier to deal with than screw terminals. They even look sort of period correct, they were harvested from some old tube-based test equipment.

Saw a couple like that that look real clean! I thought about that, found some posts made in USA at the tv repair shop for 75 cents each, bought 20 of them for good measure.

The wiring on the back side of the terminal is my guide for all the loose wires on the front end and should allow original circuit to function if the zmatic mod is undone.

The screw terminals were on the chopping block from the beginning but since i already bought them and they look nice gonna keep them for now...

I saw a 70 go for little over 200 last week, I shoulda snagged it. I was gifted an 80 chassis that would have held the guts nicely and blended right in with this one. Oh well it's a process.

I have an idea to fab a little walnut case for this someday pair and a pre underneath. It will help with presentation wire routing and may even look ok. Prob do it pretty soon after the amp is complete. Wish I had an NC router to carve out the doves and "The Fisher" for the lighted front panel I am envisioning. So the posts would def work for me too if I knew what to do with all the other wires that connect to terminals.
 
The RCA jack was faulty not short. The nut like piece of metal will not engage the thread like lines on the body of the nice looking and well marketed Chinese part. So it is not a standard part or standard size, when I use the word standard it means a few things all at once.

First and most important it serves to describe an expectation of established and documented technical specifications as found in American industrial practice as would be found in the Machinery's handbook.
Second it means English imperial units and dimensions or Merican inch fraction or decimal size.
Third, it means the expected material that it is made of is normal composition and quality and not a surprise in the cheapest possible screw you when you go to use something you need and the most basic function like a thread form is FUBAR.
Fourth, the shit is going to work.

Anyway that's what I get for not sticking to my instincts and now I have an oversized hole in the front of my 12 coats of paint 60 hour chassis.

Yes you bet your bippy I will fix it and make it look like it's supposed to be there but it was worth mentioning ad nauseum to remind myself to always buy quality parts preferably American NOS parts-sad that the good stuff is antique in many cases and little or no hope of quality returning to industry and parts any time soon.

Boutique parts are too expensive. I find most of what lures the money out of my wallet is military grade surplus when I can find it and as a function of large aircraft manufacturing operations here in Wichita some aircraft and military surplus electrical is present, I am lucky there.
 
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