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The Fisher Coronet

There isn't much to change...but change the following:

the coupling caps....they of course go from the 12AX7's to the output tubes. I think they are .033uf 400V in the SA-16.

the bias resistor and bypass cap: 150uf/150V and the resistor is 130ohms 10W I think that is the values....but you will know where (and what they are) this is because they will be connected to pin 3 of all of the output tubes.

any other small film or electrolytic caps you may find...and if anything looks "burnt or tired" I would change that too.

www.tubesandmore.com is a source for small quantities on caps and resistors. I would put in the Illinois Capactior polyprops...they are nice and they are also inexpensive.

Remember you can always go UP in voltage rating on caps and resistors...but never go down.
 
As soon as I get some more money, I'll be ordering up those caps as you suggest. Fortunately, I was able to find a schematic for the SA-16 (but not the 100-T) to double check any values.

Friday morning, I went back over both units and decided that one suspicious cap wasn't bad as I thought, but was more an issue of how the plastic coating was positioned. So, I've spent the time since then slowly bringing them up, one at a time using the lightbulb jig with the values as outlined by Outlawmws here. The 100-T has a slight buzz at max volume with no signal, but its only hearable when right up next to the speakers. I'll have to look into recapping that, I suppose. The amp is dead quiet, so much so that I had to scratch across the inputs to make sure it was even passing any signal.

Together and hooked up to my Tannoy Berkeleys (after testing with some junk speakers and measuring for nasty voltages at the outputs and inputs), they sound spectacular. For the first time, I'm able to make my Tannoys as musical as my Magnepans were. The imaging isn't quite as precise as I know my speakers are capable of, but that's minor. I'm finally getting music from outside the speakers and even behind upon occasion; the speakers are disappearing like my Maggies used to do. For just a quick listen, I ended up listening through three complete CDs without meaning to and this on a pathetic old NAD CDP.

For more specifics about the sound, the highs aren't as bright as my readings had led me to believe and bass is very tight, though a little lacking. Midrange is nice and smooth and doesn't struggle with massed choir. In fact, this is the most realistic sound I've had in a long time and when playing classical, it reminds me of the concerts I used to be able to attend back at UW. With my subwoofer hooked up, I should lose a lot of issues concerning the bass.

I will admit my setup looks a little funny, I've the two components each on their own speaker stand (those that came with my Design Acoustics D-6s) with a chunk of granite underneath to keep the heat from doing anything to the wood finish of the stands. Well, it would actually look good if I had anything approximating covers for the units rather than just open guts and had not scattered the wires all over.

Thanks, Jimmydee, for making me pursue picking up this console and getting the electronics going. I am very happy. :banana2:

- JP
 
Rebuilding Time!

I've now the resources to pursue this further and replace the caps and what else that may be suffering from age. However, as this will be my first time going through and doing more than just needed repairs, I'd appreciate some assistance and a few questions answered.

This will be in regards to the SA-16 amplifier as the 100-T has several issues and would require quite a few more parts than I'd like to spring for as a learning session.

So, be it electrolytic or ceramic, all capacitors should be replace, correct? Which type should I replace all with? Going to AES, I was unable to locate any Illinois Capacitor polyprops at all, but there are up for sale 716 series Orange drop polyprops. From my readings, I understand the latter are decent. Should I go this route instead or is there a better, though inexpensive cap available?

In further regards to this, the SA-16 has no hum what-so-ever, it is the quietest amp in my possession, be it amp, integrated, or receiver. Should I go ahead and pick up individual caps to stick under the chassis and bypass the filter quad can?

I located a schematic for the SA-16, however there are a few things that do not match up with my amp. As I look at the bottom of the amp, the bias resistor is actually a 125 Ω 7W and the bypass cap is 75 μfd 25v versus the 130Ω 10W & 150μf/150V listed in the schematic. Do I rebuild it as it is or convert to the schematic values?

Another mismatch is with the coupling caps. The schematic calls for 0.033 μfd caps, but in the amp, the caps are 0.022 μfd ceramics. Again, which do I do?

Finally, are there any other things I should look into changing out? For instance, which of these carbon film resistors are in particularly vital positions and should be changed out for something of higher tolerance? I understand that removing all of these carbon films has a habit of killing the sound, so I'd like to avoid replacing all of them if possible. Any mods I should also consider to improve this amp if at all possible?

Well, thanks for taking the time to help a relative tube audio newbie.
- JP
 
Use 130 Ohms - 125 is not a standard value. Larger is better for the bypass too. I'd use .033 caps - but I'd make sure I had .022s on hand as well, as it's a common value I use anyway. I only change resistors if they're off value or noisy. Mouser has Xicon polypropylenes which are smaller than the Orange Drops... but no .033...? Use 600 or 630V caps.
 
Fortunately, the chassis is 1 3/8" deep and fairly open, so cap size shouldn't be a factor in the bypass cap range. I'm more concerned about balancing what will offer up the best sound for the price in this amp and of course, doing it as 'right' as I can manage. From what I've heard this amp do so far, I've high hopes.

I just don't understand why the amp would vary so much to the schematic, which is purportedly just a redrawing of the original 1959 schematics. The value differences look original and I've no reason to believe anyone's dug into these. Even the tubes are all original Fisher branded.

Well, the holiday weekend is upon us, so any ordering will have to wait until next week, so I've plenty of time to think about this.

Thanks for chiming in. Btw, I've always liked your avatar, very cool looking.
- JP
 
Upgrading to .033's is no problem as Tom said...Illinois Polyprops are available through AES...but their website kind of sucks. I recently ordered some from them..but I have a print catalog. Actually I just looked...they are there. Click "capacitors" and than click "tubular" and then click "metalized polyprop". That is the Illionois Caps.

I take it you don't have access to a scope??? If you do check the original can cap...most likely it is fine. If you want to change it AES has new production 50/50/50/50 @350V can caps for $33.95. It saves all of that underwiring. If I remember correctly the original is 40/40/40/40 @350V. Just make sure to ground the cap either by soldering one of the tabs to the chassis (the way the factory did- but you need a serious size soldering iron a 100W with a big tip), or running a wire from one of the tabs to a grounding point on the chassis.

Cermaic caps don't have to be changed for "age" reasons but they tend to sound crappy. Replace if you wish (change the coupling caps to film) or leave them in.

The carbon resistors are most likely fine, check voltages and see if anything funny change it. Also...you can get new carbon film resistors anyway...so if you want just change them all...the SA-16 is simple enough that this will not take very long- afterall it is not a 500C!!!

Changing the bypass cap to 150uf is probably fine. Again check your voltages afterwards and see if everything falls into spec.

Fisher made many changes to their units...it is a good reason to get an official Fisher service manual for your proper serial number block.
 
Thanks, JimmyDee. You're right, that website is poorly designed and a previous search revealed not one mention of "Illinois." I was able to order up most of the caps just now, though I was unable to find a cap or bias resistor that matched up in the values either in the amp now or as you suggested, without stacking a bunch of odd ones. So, I'll grab them somewhere else to try to keep the layout fairly clean.

After this amp, I'll dig into the 100-T, which also has developed a flaming rectifier tube (entertaining to watch, but not something I'd let run when happening). Now that's a great deal more cluttered, but not bad considering. If the 500s are anything like the defunct 550-T I have here, I shudder at the thought of refurbing that.

- JP
 
The sparking rectifier tube is always fun...there is a chance it isn't toast (if it is a Mullard...I have had several give me a fireworks display and still work).

Most likely it is a shorted can cap...this is common on Fisher gear from that era. At worst it is a bad power transformer.

Discharge the can cap that is connected directly to the rectifier tube. Then de-solder all the wires going to the positive sections and use an analog meter to check it. All of the ones that have given me a firework display were DEAD shorted so it was obvious with a meter check.

I did have a unit that after replacing the can cap, I still was getting a sparking rectifier. It turned out to be the shitty chinese (current chinese offerings are much better- this 5AR4 was from the early 1990's) tube.

The 550-T is a nice unit...you should get that running. But they take lots and lots of work. I can restore about 3 500-C's in the amount of time it takes to rebuild a 550-T!!!
 
The rectifier tube isn't giving me a fireworks display (had an old type 80 in an equally old Hallicrafters Sky Buddy that gave a 4th of July display shortly before it exploded, now those were fireworks), it's just living up to the name "fire bottle" by being filled with a red flame. I assume this is due to atmospheric gases getting in someway spoiling the vacuum? The tube, as all the tubes in both these pieces, is an original Fisher brand 6V4 (hopefully that's a rectifier as I think it is, don't have a schematic).

It's a sad thing, really, as the 100-T was working fairly well after I brought it up on the poor man's variac, it had a slight hum equal in both channels and the sound was a bit dark and muddied -- I figure due to soft tubes and tired caps -- but I played it for hours with no change. Then I let it set the better part of a week and when I turned it on, these problems arose including the strong hum in the right channel only. Guess something was ready to go anyways.

I'll put it on my list of to-dos, fairly close to the top. Still, I'll probably have to wait on it as the cost of all the caps needed isn't as low as it was for the SA-16. 'Nuther problem is that there are three can caps in this, so it's not quite going to be the easiest fault to track down, or the cheapest.

The 550-T I picked up at a hamfest back in June for $5. I should've known there'd be issues due to the price and the lack of screws and feet for the case (someone had been in there before), but it was my first Fisher and I wanted to see what all the fuss was about. There's no sound, nada, out of it either via speakers or headphones. It's been a while, but I don't recall there even being any voltage on the terminals. That thing is a maze inside, for an early solid state rig, I'm in awe with just how much they managed to cram in there, easily twice as much as a late '70s Pioneer. Hence why it's still on my to-do list, I'm not even sure where to begin. I can definitely see why you can repair the 500s faster, but then again, you aren't exactly new at this.

- JP
 
Well, since it doesn't look like the image database will be repaired as soon as I hope, I'd better post some pictures for those interested.








These were taken before I cleaned everything up and they did clean up well. However, I found a little bit of white stuff on the coating of the SA-16 where I suspect the previous owner cleaned up with a little bit of solvent. Can I just put some light 3-IN-ONE oil on the chassis to take care of this oxide, as I believe it is, or is there something better for that to clean up the chassis and keep it from corroding?

Thanks,
- JP
 
Interesting. The caps arrived today and I've just finished up recapping one channel on the amp, leaving the other as is for comparison purposes. The result? Almost no treble on the recapped side. The values match up to what I pulled out, aside from from upping the bypass caps to 0.033 from 0.022 as recommended.

Dun think I pulled anything loose or overheated something, but I've not worked with polyprops before.

- JP
 
Nevermind, I finally managed to track down the problem in a little tuned circuit on the side. It's been the better part of a decade since I've done this kind of work, so it took a while to dredge it back up from the back of my memory. For what it's worth, the recapped polyprop side now sounds a great deal smoother than the other with only ceramic caps, though the lack of hash now makes a faint hum audible.

- JP
 
Ok, I've just gone about recapping the other channel and discovered that the caps I ordered (I ordered Illinois Capacitor metalized polypropylene) are of a mixed type of the same value. I've some 0.033s with MPW and H 24 printed on them of which I understand the MPW to stand for metalized polypropylene, what I ordered. However, most have H 13 and MWR, which a quick Google search reveals to be metalized polyethylene. What's the deal here? Is the information I found incorrect or did Antique Electronic Supply send me the wrong stuff/cheat me?

- JP
 
Hmm, this will be the sixth continuous post to this thread made by me. If anyone has something to chime in, it would be appreciated.

At any rate, today has seen my first tube rolling and unfortunately, I liked the results. This T-giving I managed to snag my old Heathkit TC-2, which though having seen better days (thanks to raccoons, the roof of my father's shop where this was stored gave way and soaked it thoroughly) still works just fine. According to it, the 6BQ5s in the SA-16 have reached the end of their life and read only 20%. However, when I checked the Dynaco labeled 6BQ5s in my under-repair SCA-35, I got a strong 80% reading. So, I swapped out a channel in the SA-16 with the Dynacos, which show a healthy blue glow at the bottom of the plate and provide much more amplification than the tired Fisher labeled tubes. Comparing the two channels in mono (levels adjusted to match), I can definitely say that the Dynacos sound a great deal better and much smoother. The midrange now with my Tannoys now betters the previous record holder for good midrange, the Sonic Impact T-amp, by a huge margin.

So, as I do plan to finish repairing my SCA-35, just as soon as I receive a new filter cap and have solved, I hope, the problem, I am going to need some new 6BQ5s for this SA-16. Any suggestions on where I can snag some good, nice sounding tubes for a bargain?

Thanks,
- JP
 
I'm using EI EL-84's in a push-pull amp, they seem good sounding and have held up fine over the last couple years.
I would like to try the EI elite EL-84's sometime......

I don't really have any idea on the sonics with other new makes and brands of 6BQ5/EL-84's.
 
EL-84.

Lots of good, new production tubes out there on the cheap. I would suggest either the Russian military el84/6bQ5's, or the JJ el 84's.

Paul
 
Thanks for the tube suggestions. Where would be a good place to grab said examples? Also, do I need to pick up matched tubes with this little amp?

I almost thought I lucked out last night in regards to the tubes when I remembered that my Fisher Promenade, a 6BQ5 amp if what I was told is correct, was chock full of Amperex Holland labels and the stray Mullard. I pulled the two easy to get to outputs and tested them, both showed a short, dang it. What would cause this? Any chance these are substitutes that just don't measure correctly as EL 84s?

Thanks.
- JP
 
Charivari said:
Thanks for the tube suggestions. Where would be a good place to grab said examples? Also, do I need to pick up matched tubes with this little amp?

I almost thought I lucked out last night in regards to the tubes when I remembered that my Fisher Promenade, a 6BQ5 amp if what I was told is correct, was chock full of Amperex Holland labels and the stray Mullard. I pulled the two easy to get to outputs and tested them, both showed a short, dang it. What would cause this? Any chance these are substitutes that just don't measure correctly as EL 84s?

Thanks.
- JP
Click to expand...

JP,

Not sure what would cause the short. I believe the test settings are the same on these tubes as for el84. If they are measuring shorts, I would be hesitant to use them. Especially with good new tubes available for not too much $. Not sure on your budget, but you can get a nice matched quad for under 40 bucks.

As for a source, I like JimMcShane:
http://pages.prodigy.net/jimmcshane/tubes.htm

Get those tubes in and get that sucker going!
Paul :thmbsp:
 
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