| akimball442 |
Well, I think (hope) I just got a once in a lifetime deal... Is anyone here familiar with the Fisher (TA) 600 model receiver?
I just picked one up. This is an interesting unit though. Built into a console (called the custom module) Is the receiver, and a drawer pulls out to reveal the barely used garrard turntable. Both of the original speakers are included also... along with all of the books that arent even yellow because they've been in an enevelope since 1959. This unit was sold as a complete set, called the model 90.
There isnt a mark on any of the woodwork and I got it for $100.
This unit is 100% original, and has all of the original Fisher branded tubes, most of which say made in Gt Britain, and appear to be mullards!
First the good: The tuner in this unit is amazing, on both FM and AM with only the built in antennas, and other radios in the house barely pick up anything. So I'm very pleased with that. Both of the magic eye tubes work, and work well. The dial lights up perfectly, and as I said, this is in new condition.
It has 7189 outputs, for a total of 20 watts per channel.
Now the bad: I'm not impressed with the sound of it at all. It's not really AWFUL... but both of my Eico's (the ST70 and ST40) far out perform it both tonally and power wise, and my little Magnavox 9302 will blow it out of the water as well.
This does not make sense to me, from what little I can find about it, it was very high quality (which is obvious just in the design) and people seem to love their Fishers.
The Bass is a bit much, even set flat with the loudness control off. The upper midrange is a bit overpowering as well, and the treble could be better.
Should I just dig in and start replacing all of the coupling caps.. or are these normal Fisher characteristics? I LOVE the look of this thing, and want to use it... I can live with the reduced power, but it needs to not clip so early, and the tone sure needs to impress me more.
I'll add that all of the controls work perfectly, are noise free-- this came from the original owner who had it in his dry, smoke free home.
Anyone with any ideas, or anyone who has one please reply! I'm interested in your opinions. Pictures to follow if anyone desires. |
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| anatech |
Hi akimball442,
Coupling caps!!!! Replace them !!
Filer caps !!! Replace them !!
If you don't do this, the unit may fail. Don't even run it.
I have a Fisher and it sounds nice. Don't expect this to run properly until you have fixed these problems. Also, Fisher liked to use Selenium rectifiers, you must replace these with silicon diodes and include some extra resistance to lower the rectified voltage.
What I've said applies to all old equipment, especially tube equipment. It's very sad to see a burned out transformer because someone felt they knew better. Even older Marantz solid state (and the others) need to be restored (this is by no means a repair).
I also own some nice Eico equipment, love them. Anything I run has been restored. Please don't kill your gear.
-Chris |
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| valveitude |
Based on the description of the sound, something is most definitely wrong. As an owner of an 800, I can tell you that this vintage of Fisher may not be the last word in accuracy, but what little errors there are of are of a euphoric nature..a very musical presentation.
When I first got my receiver it sounded like cat scat. A replacement of the coupling, as well as the bias supply caps, and the electrolytic cathode bias caps was the first step. I also replaced the selenium rectifier in the bias supply.
A few dollars in parts, and an afternoons work is all you need for an outstanding receiver.
Casey |
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| Tom Bavis |
| If you don't have a schematic, it's in Sams Photofact folder 478-10. Not in my collection though... |
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| akimball442 |
I do have a schematic, although it isnt EXACT. For example, it's definately the right model (TA-600), however, my unit has a line level center output.. which according to the owners manual is mono. I was curious as to which part of the amp this was derived from, I'm assuming it comes right after the preamp, because the owner's manual says that the volume and tone controls control it. The schematic does not have the center channel.
All of the tubes and other components are the same from what I can tell, so I think it'll be useful for repairing this amp. I'll check when I get home (I am at work right now) as to which number is on the schematic. Thanks for posting the SAMS number.. The schematic I have is a copy of the SAMS' schematic, so I'll see if they match up, or whether the one posted in this thread is a different one.
I had figured that this unit would need some work, given it's age, but I'm wondering whether or not it's safe to leave the tuner sections alone, as they function perfectly. I'll replace all of the power caps, and coupling caps, and check the condition of the resistors.
Someone mentioned a selenium rectifier... I'm wondering if this has one.. as I said, I do not have the schematic handy, but I know it has two tube rectifiers. One is a GZ34, the other is a smaller one, I forget which. EZ90 maybe..
Thanks for your posts, I'll keep this thread updated.
Aaron |
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| anatech |
Hi Aaron,
You may find selenium rectifiers in the bias supply and the heater supply. I haven't got this schematic, but my 400 C preamp uses a DC heater supply (25 VDC, series strings of two heaters in three sections for 6 tubes).
Your Fisher should sound very good.
-Chris |
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| Eli Duttman |
Aaron,
Googling for a schematic turned this up, which contains some interesting info.
The 2 rectifiers are a 5AR4/GZ34 and a 6V4/EZ81. Both are used to generate positive rails.
The O/P tubes are self biased. The phono section heaters are in the O/P tubes' bias circuitry. There is no negative supply in the unit.
An external MPX adapter is required for FM stereo. If you don't have the adapter, Steve Bench "rides to the rescue" here.
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The 20 WPC rating says the O/P tubes are 7189As, which are rare and EXTREMELY expensive. IMO, while you are recapping, you should make the changes needed to use 7189s as the O/P tubes. The Russian 6p14p-ev/EL84M is a true 7189 equivalent that's affordable. 17.5 WPC is not at all shabby, when long term serviceability is taken into account.
When O/P dissipation is reduced to a level suitable for 7189s, you can no longer place 12AX7 heaters in the bias circuitry. An external regulated 12 VDC supply will have to be built. |
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| anatech |
Hi Eli,
Thank you. It looks like my 400-C and FM-100 combo. Knobs and all!
-Chris |
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| akimball442 |
The one I have is slightly different, for example, the antenna connections are not mounted horizontally with the screw connections on top as shown in the photo. Mine are oriented like the speaker connections, and line jacks, horizontally on the back of the unit.
Also, mine seems to have just plain 7189 tubes... not 7189A. I wonder if this could be a problem?
The schematic I have does not specify "A" tubes either, just 7189... same applies to the label on the back of the cabinet.
Furthermore, there is NO solid state recification of any kind in this unit. I have gone over the schematic from left to right using a ruler... and all rectification in this amp is done with tubes.
The phono preamp does get it's heater supply in the fashion you mentioned though, interesting. A good idea too.. I need to do that to my blessed Eico ST70- DC heaters. The phono stage in that thing is pretty nice, but so noisy..
I'll be the first person to take a screwdriver to the bottom of this unit since it left the factory in 1959... COOL! I don't think I own any piece of equipment that someone else has not repaired or butchered over the course of time. This thing is truly 100% original, and I cannot wait to hear how it sounds when I finish.
Aaron |
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| anatech |
Hi Aaron,| quote: | | Also, mine seems to have just plain 7189 tubes... not 7189A. I wonder if this could be a problem? |
No. There may not be any real differences that apply to your amp. What you will buy these days as a replacement would be a 7189A. I have a couple amps that need those type of tubes.
| quote: | | Furthermore, there is NO solid state recification of any kind in this unit. |
Cool. Relax then.
| quote: | | A good idea too.. I need to do that to my blessed Eico ST70- DC heaters. |
No you don't. There is nothing wrong with AC heaters. I prefer them. If you want to really improve things, bias them up 30 ~ 50 VDC from ground. Lose the hum balance pots (that are grounded). You can leave them in the chassis.
| quote: | | The phono stage in that thing is pretty nice, but so noisy.. |
Phono stage where? My Fisher 400-C has the phono stage tubes mounted on rubber grommets. :cool:
-Chris |
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| akimball442 |
Haha, after I re-read things, I wasnt getting snippy about the rectifiers, I hope nobody took it like that. I think I was just excited.
I was referring to the phono stage in the Eico when I said I liked it, just noisy... not the Fisher, I was making a comparison in the heater supplies.
I shouldnt mix and match things so much I guess. I have not formed an opinion on the phono stage of the Fisher yet, although it is definately very quiet, but I have to get the amplifier sounding good before I can decide how it sounds.
Aaron |
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| Eli Duttman |
Guys,
Check the data sheets. The 7189 is rated for the same plate dissipation as the 6BQ5/EL84, but the 7189 can take a higher anode voltage. The 7189A is rated for both higher plate voltage and higher plate dissipation than the 6BQ5.
6BQ5 Data Sheet
7189 Data Sheet
7189A Data Sheet
Tube World is asking (sic) $175 for Toshiba factory matched 7189A pairs. That's $350 for a new set of "finals". Even at the high price, the rare and out of production 7189As will go fast.
Jim McShane charges $21.50 for a matched pair of EL84Ms, which are 7189 equivalents. IMO, making the changes necessary to use 7189 equivalents is obvious. |
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| Tom Bavis |
Some fine print on the data sheets... 7189 is rated for 400V and 12W "Design Center Values". 7189 is rated 10% higher for both, but it's "Design Maximum". These are just about equivalent ratings.
The 7189A DOES have connections defined for two pins that are "IC" - internal connection - on 6BQ5 and 7189. Since these pins are defined as "Do not use" on the 6BQ5, it should be OK to use 7189A for 7189 (and vice versa). I believe the Russian ones DON'T use these pins anyway - and not all manufacturers were consistent - tube testers may or may not show "short" on pins 1, 2, 6, 8, depending on brand.
I have a set of the Russian 7189s in a Lafayette receiver, and they seem to be happy at 420V or so... |
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| akimball442 |
I was not disagreeing about the specs. I wonder if Fisher's rating of 20WPC was high? Should it actually be the 17.5 Watts?
As I said, everything is stamped 7189, including the chassis where the tubes go, rather than 7189A... and all of the literature, schematics, etc reflects this. However, it also all says 20 watts per channel.
I guess my question is this. I don't care if it'll only do 10 watts per channel. If its really only 17.5... then that's perfectly fine. What I am wondering is if there is an ERROR... and either it should be 7189As, and I DO need to modify things to use the tubes that are in it (which I kind of doubt)... OR- can I just leave the parts values alone and replace the caps and enjoy the stereo.
I never said it had 7189As to begin with. Someone based that on the specs of 20 WPC, which makes perfect sense to me if you look at the Data sheets. But I believe the amp was designed to use plain 7189s, because it has the original outputs, which are Fisher branded 7189s, the chassis SAYS 7189, as does all of the paperwork. So I'm confused as to why I'd need to modify anything (?)
Perhaps I'll scan the schematic and attach it at some point in the near future. |
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| anatech |
Hi Aaron,| quote: | | I was not disagreeing about the specs. I wonder if Fisher's rating of 20WPC was high? Should it actually be the 17.5 Watts? |
Probably. The rating in the tube manual is at a certain distortion with no feedback. Fisher is using feedback and may rate theirs at a different distortion rating. So it may be the same thing. Don't worry about it. Besides, you will not hear a difference between 20 watts and 17.5 watts.
| quote: | | So I'm confused as to why I'd need to modify anything (?) |
I think the previous post indicated that no mods were needed. Relax.
| quote: | | Perhaps I'll scan the schematic and attach it at some point in the near future. |
that would be great! Would you mind sending me a full resolution copy please? bhomester at gmail dot com.
-Chris |
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| Eli Duttman |
Aaron,
FTC regulations were not as tough in 1959 as they are currently, when claims about the performance of consumer electronics are made. It seems Fisher was "creative".
| quote: | | I'm confused as to why I'd need to modify anything (?) |
7189 plate dissipation should be limited to 12.5 W. per tube. It's a matter of reliability and service life. Changes in the operating conditions may be needed to stay inside that limit. If the operating conditions change, an external DC filament supply is needed for the phono section tubes.
Regulating 7189 screen grid B+ is something you can look into, as linearity will improve. |
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| anatech |
Hi Eli,
Does the current circuit operate the outputs outside this safety limit? I can't say as I have no information on this model.
-Chris |
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| akimball442 |
According to the spec sheet, the 7189 can run as high as a 400V plate voltage, this amp runs them at 380V. (According to the schematic... I still havent had a chance to take it apart and probe around in there.) This weekend I'll get to doing that, probably Sunday afternoon. I'll have to check and make sure it's not running too hot..
It could well be, mains voltage here seems to hover around 120 volts. If it was designed to operate at 115 or 117, chances are its running a bit on the hot side, and fast approaching the 400V. |
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| Eli Duttman |
| quote: | Originally posted by anatech
Hi Eli,
Does the current circuit operate the outputs outside this safety limit? I can't say as I have no information on this model.
-Chris |
I don't know. I too am hoping to get my mitts on a schematic. Fisher was not stupid. It's quite possible that all is well, electrically.
The advertising copy has me wondering what is really going on. "Hype" aside, that IS a good looking unit. After overhaul, I expect it will also sound GOOD. |
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| Tom Bavis |
Fisher often operated the phono tubes below nominal heater voltage, for lower noise. If they ran 130mA , that would be about 13W per tube (guessing 422V on plate and 22V on cathode).
A matched set of output tubes is VERY important in this amp.
I'd also be interested in a scan if you get to it. |
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| anatech |
Hi Eli,
I agree. Fisher was well designed. I do not think they played with the numbers or designed it in a way that was unreliable.
My Fishers and all the ones I've rebuilt sound great as well.
-Chris |
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| akimball442 |
I guess what is shocking to me is that from what I am getting here, nobody has really seen this particular model.
Anyway, I'll take the schematic to work and scan it. My scanner is not behaving.
It's very large, so I'll email it to those who want it, it'll be two separate files, possibly 4 depending on how the one at work treats me. Feel free to reply here or email me with your email addresses. I will not get the chance to do this until probably Friday afternoon, or even early next week, work is hectic during the summer in the school bus business that I work in. I'll be on the road the rest of this week, at least. |
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| anatech |
Hi Aaron,
If I had ever seen one, I would have grabbed it. Many may have died unseen inside wood boxes.
You should see my 400-C preamp. There aren't too many of those around either. Doesn't bother me in the least.
-Chris |
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| Zero Cool |
I have been looking for a unit like this for YEARS!~ But i have never been able to find the exact model.
When i was a kid my dad had something very very close to this that he built his own case for. years later i ended up with it.
The odd thing was that the Fm was mono unless you had the adapter, but the unit i had, had a stereo setting where Am was on one channel and FM on the other. I have heard from several people that is how they did stereo at first before multiplexing became the thing.
This looks smiliar to the unit we had. the knobs on ours were different and i swear it had meters instead of magic eye's. I have never been able to figure out what model it was however. My family has pictures someplace with it in the background. one day i will find those photos and scan them.
My dad said he got it from a radio station where it was used as a off air monitor.
Zc |
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| anatech |
Hi Zero Cool,
Yes, several early "stereo" units recieved one channel on FM and the other on AM. I have some like that around here. My MPX board for my Fisher FM 100 was wrecked when my dad kicked the 19 KHz transformer off. Never to be found again. I do have a pair of Eico demodulators for use with .... my Eico tuners. There were a popular accessory.
Also, would you please PM me? No parts yet.
-Chris |
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| loadrecords |
Hello,
I am new to this board: My name is Ben McOsker.
Just found a fisher ta600 in the trash. Looks to be in all right condition. Needs the 7189 tubes replaced. Also got a gz43 just in case.
I want to replace the caps and the selenium bias parts in this unit. Anyone have a list of appropriate new parts numbers i can use to start the process of getting this amp back up and running.
Best,
Ben McOsker |
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