The Fisher TA-600 Rebuild Thread

Now first a little bit of background how this Fisher came into my possession.

As many of you probably saw a few months ago I purchased a minty, completely Audiodon'ed Fisher 500C from fellow AK'er gigabyt. Due to ignorance on my part assuming all professional packing stores were like my local UPS store (which is fantastic I might add), it was marginally packaged and severely damaged in transit. You can see the carnage HERE. Long story longer, I sent it back to Gigabyt who took on a 1 or 2 month battle with fedex who denied claim after claim. They eventually paid up due to the perseverance of Gigabyt. He took the receiver back to it's original restorer Audiodon to see what could be made of it. Audiodon's since brought it back to life HERE and it looks to be going to another happy home soon. It wasn't meant to be leaving me with the substantial sum of money in my pocket to look for another. Maybe it was the soldering iron Gods lashing out at me for going with the quick easy fix.

Moving forward, out of the blue AK'er Apurcell22 PM's me to let me know he has both a Fisher TA-600 and Fisher 800-C that are excellent cosmetically in need of love. They have both been worked on by previous owners but appear to have never been finished all the way through. We discussed a deal and I parlayed my money into both units. Right as the deal is finalized Apurcell22 encountered some problems on his end delaying shipment due to circumstances out of his control and no fault of his own. Apurcell22 packs them bulletproof and they eventually arrive at my doorstep looking like a million bucks. :thmbsp:

Now onto the TA-600:

The Good

1. It is in fantastic cosmetic shape. The only one I think I've seen better is TheRed's TA-600 residing comfortably in it's original console.

2. Other the output tubes which were a mixed bag of 7189's (Telefunken, GE, RCA, Mullard), the rest of the tubes all appear to be original Fisher-labeled.

3. Inspecting underneath, someone definitely was inside noticing all the orange drops that appear to be older. While they did an admirable job attempting to make the unit functional, they passed on a lot of caps that should of also been replaced. They replaced parts with appropriate values and didn't appear to hack things up.

The Bad

The 5AR4 rectifier arcs once the voltage is brought up high enough on the variac. Bringing it up without both rectifiers in brings all the tube's filaments to life. I inserted the 6X4 rectifier to see what would happen. The tuner/pre-amp came to life. Judging by by the tuning eye, both AM and FM had very strong reception on both bands without an antenna even being connected. I even tried a known good quad of ruskies to see if the previous mixed bag 7189 quad had a tube with a short in it. Still arcing. At this point the only thing I can think it must be is a can cap.

Here's a picture of what we're dealing with underneath. The are a bunch of little caps buried pretty well.



Stay tuned, I will be posting before and after pics of each section I recap. I will be using 716p's and replacing even the newer caps.

Kory

I just finished reading the before and after threads on the 500C. What an amazing job Audiodon did on the receiver to bring it back to life. I just can't imagine how you must have felt when you opened the box and saw it destroyed. I'm the pround new owner of a restored 500C and I'm just so thankful that the man who restored it knows how to pack audio equipment. He double boxed it and used about 100 yards of bubble so it made the trip from L.A. to Albuquerque in perfect shape. Good luck on your future projects. I'll be looking forward to seeing your future postings.

Here is the bias supply mod we talked about in the other TA thread. Per Tom B 10-03-09
"If you have the Sams schematic, what you want is the 15K resistor R162 - lower it to reduce the idle bias. Adding 220K in parallel will give 14K, 100K in parallel will reduce it to about 13K, and will reduce the current proportionally. 12AX7s should be OK at 20-22V on the heater."

I noticed that you are using a 6X4 rectifier for the lower voltage B+. I'm almost certain that the TA-600 uses a 6V4 for that position. Mines does, all schematics I've seen reference the 6V4

Great thread!

Thanks for the kind words ssmith3046. Glad to hear you are enjoying your 500C. I wouldn't ever part with it if I were you.

Well this morning I decided to tackle a couple caps. Seeing that I didn't have a ton of time to work, I decided to replace a few coupling caps and a small lytic' nearby.

Before Pic



Next I replaced those 3 older orange drops with (3) 0.1uf 600V 716p's. I also replaced the small 25uf@6v lytic with a 25uf@25v lytic. In the process of trying to squeeze the bigger orange drops in there, I broke the lead to that ceramic cap and another one of the resistor's leads nearby that I moved feels little flakey. Both will have to be ordered and replaced appropriately.

Pic of work

dsndblm said:

Here is the bias supply mod we talked about in the other TA thread. Per Tom B 10-03-09
"If you have the Sams schematic, what you want is the 15K resistor R162 - lower it to reduce the idle bias. Adding 220K in parallel will give 14K, 100K in parallel will reduce it to about 13K, and will reduce the current proportionally. 12AX7s should be OK at 20-22V on the heater."

I noticed that you are using a 6X4 rectifier for the lower voltage B+. I'm almost certain that the TA-600 uses a 6V4 for that position. Mines does, all schematics I've seen reference the 6V4

Great thread!

Click to expand...

I'll bet it's a 6V4 and I was just mistaken off the top of my head. I was just too lazy to turn over this beast to double check. Thanks for the bias mod. I do have a nice sam's photofact in hand which has been a nice help.

Kory

I will add you will probably notice where I pig-tailed some parts. I normally try not to but there are just certain places it makes sense to me. While it might not be easy on the eyes, if done correctly will be just fine.

Kory

I am always amazed that the TA-600 gets so little recognition. SOUNDMADNESS refurbed my TA-600 which I bought from another AKer who had it in constant service and it rivals my HF-81, LK-72 and Stromberg Carlson offerings.

The 500C is a keeper, kpaxfaq. I now have five transistor laden receivers sitting idle. My KLH Model 5's have never sounded better. I have a pair of AR-2ax's I might try out with it too. I caught the Fisher bug after I bought a X-100-C to use in a system for my bedroom. I still amazed at how good the 100C sounds too. I have a pair of New Large Advents hooked up to it.

kpaxfaq,
Are you sure those orange drops are 716P? They look kinda too fat to my eyes.
The only minus on orange drops in my estimation is that the leads are quite thick and not easily pliable (or pliersable).

Kory,
Nice to see you getting started. I can't even see my bench yet. That fire has set my life back probably six months! I hope you enjoy the fishers!
Al

audiodon said:

kpaxfaq,
Are you sure those orange drops are 716P? They look kinda too fat to my eyes.
The only minus on orange drops in my estimation is that the leads are quite thick and not easily pliable (or pliersable).

Click to expand...

Don,

They are 716p's and they are fat indeed! They are bigger than expected. I've only used 400V 0.1uf 716p's before which are about the size of what was there previously. (Previous OD's present were 600V rated) I squeezed them in though.

Here's what I'm using from AES

apurcell22 said:

Kory,
Nice to see you getting started. I can't even see my bench yet. That fire has set my life back probably six months! I hope you enjoy the fishers!
Al

Click to expand...

Al,

Sorry to hear about the continued setbacks. You never know maybe one of these Fishers might just make it back your way sooner than later. :thmbsp:

Kory,
It's no big deal. I just have way to many projects. I need to fix a marantz 510m, finish a get set go, an akido, trouble shoot an st70, build an f5,build a jonokuci. You get the idea.
Al

Actually, I bought a couple dozen last time and it's now been a couple of years. They seem rounder than I recall, though the marking's clearly right. Could look big under that chassis too. I'm not familiar with that particular chassis type.

With the unit running, if you put a meter across the two caps, you'll notice a considerable difference in voltage across the two tubes of a push-pull pair.

It's a bit tighter under the hood of that 600 than it is under a 500C. I'll be following this one for sure.

Jailtime said:

It's a bit tighter under the hood of that 600 than it is under a 500C. I'll be following this one for sure.

Click to expand...

It's hard to tell in that first photo but the chassis is unlike the 400/500/800 series because it has two depths. It's twice as deep in the tuner section towards the face plate than it is at the rear. The black cardboard cap can on the right is at the rear of the deep section and everything south of it and the thick black shielded cable running laterally is in the shallow section of the chassis.

This increases the challenge of putting filter caps inside the chassis and leaving the external cans just for show. It's hardly an option unless you get really creative.

kpaxfaq said:

The only one I think I've seen better is TheRed's TA-600 residing comfortably in it's original console.

Click to expand...

Once yours is up and running I think the title of "Nicest TA-600" should rightfully be bestowed on yours. Mine's not so pretty underneath: it shows evidence of very heavy use and quite a few repairs with some indifferent soldering. I'm very impressed with how clean yours is underneath - it hardly looks used at all.






Interesting that yours has that cluster of three rectilinear, high-wattage resistors in the place of what, on mine, looks like a deep-fried stick of gum which is in fact a huge wire wound resistor. I wonder if yours is a later production example. Mine is serial no. 21894 and has a June 1959 date stamped on the back of the faceplate.

TheRed1 said:

Once yours is up and running I think the title of "Nicest TA-600" should rightfully be bestowed on yours. Mine's not so pretty underneath: it shows evidence of very heavy use and quite a few repairs with some indifferent soldering. I'm very impressed with how clean yours is underneath - it hardly looks used at all.

Sometimes beauty is only skin deep.​

Interesting that yours has that cluster of three rectilinear, high-wattage resistors in the place of what, on mine, looks like a deep-fried stick of gum which is in fact a huge wire wound resistor. I wonder if yours is a later production example. Mine is serial no. 21894 and has a June 1959 date stamped on the back of the faceplate.

Click to expand...

Red,

Mine is serial number 32195. The date on the back of the faceplate is June 23rd, 1959. The schematic shows that above the 2200ohm 7 watt resistor should be a (1) 140 ohm 10 watt one. In mine there is (2) 300ohm ones paralleled which gets in the ballpark. I'd bet they used what was available on the line at the time.

Stay tuned, the irons are heating up, the coffee is brewing, it's snowing outside, and I don't have to work until 4pm. :thmbsp:

Kory

kpaxfaq said:

Stay tuned, the irons are heating up, the coffee is brewing, it's snowing outside, and I don't have to work until 4pm. :thmbsp:

Kory

Click to expand...

Solder is about to be slung!

TA-600 is 7189 based, right?

Jailtime said:

Solder is about to be slung!

TA-600 is 7189 based, right?

Click to expand...

Yes