Fisher 220T...

knockbill

Lunatic Member
Just picked up a Fisher 220 receiver at Hamfest today,,,

I started on AK with all the help I got here, recapping my Sansui 800, but soon after got hooked on tubes...
Never had a Fisher piece before, but this doesn't look too complicated, seems a lot of the transistors plug into sockets...
What kind of performance can be expected? Similar to the Sansui? Can the power amp, and preamp sections be separated (without major surgery!!), to use it as a pre w/ tube power amp?

I did a little testing/measuring today,,, there is static, probably leaking PS caps when its turned on, and also when it is shut down...
Used its tuner as an input, which really sounds good,,, main problem I see immediately is, the right channel is about 1/3-1/2 volume of the left... Using the balance control can make them even, but the L is much louder...
There are not too many V readings on the schematic, so I got PS readings, which were pretty close to schematic... Also, compared the 9 pins on each amp board, the R side board in the amp, reads slightly higher than the L...
Any thoughts how to find the problem, without just changing everything? This might be a good exercise in troubleshooting...
Once the caps charge up, the amp runs pretty quiet, other than the low R side output problem...

Schematic/manual is at.... http://www.hifiengine.com/manual_library/fisher/220-t.shtml

Regards,
John
 
What happens with the relative volume levels with the STEREO-MONO switch set to MONO and the Balance control centered? This would isolate the problem to before or after the balance control.

The turn on/turn off "static" could be from the fact that the output is coupled to the speakers through coupling capacitors. Those have to be charged to half the supply voltage and the charging path is through the speakers. Is the "static" a loud "WHOOMP" when turned on and a lesser "whoomp" when turned off? If possible, look at the woofer cones at turn on and see if they move violently for a second or so.
 
What happens with the relative volume levels with the STEREO-MONO switch set to MONO and the Balance control centered? This would isolate the problem to before or after the balance control.

The turn on/turn off "static" could be from the fact that the output is coupled to the speakers through coupling capacitors. Those have to be charged to half the supply voltage and the charging path is through the speakers. Is the "static" a loud "WHOOMP" when turned on and a lesser "whoomp" when turned off? If possible, look at the woofer cones at turn on and see if they move violently for a second or so.

Thanks for replying,,,
I did try the Mono-Stereo switch, Mono more or less centers the volume level...
No Whomp at start up,, more like a scratchy, staticy sound,,, very similar to the Sansui, (but you didn't hear that!,,,and recapping fixed it)... Didn't notice the speakers surging...

The V readings on teh amp boards are a few tenths of a V different, board to board,,, could those 200/35V coupling caps need replacing? I'm sure they do, as it doesn't look easy to get to em!

Regards,
John
 
Voltage changes of tenth's of volts is nothing to worry about. No two caps, resistors, transistors, or even wire leads will result in the exact same voltage. If your voltages are within 10% of nominal (schematic voltages @ 117vac input) the voltages are generally ok. IIRC some transistors on the 220-T are germanium so their E-B voltage is about 0.3v vs. 0.6v with Silicon transistors. Look at the differences between the Emitter and the base voltages. It should be about 0.3v difference. Silicon will be 0.6v.
Germanium's transistors compared to Silicon are noisy. On the Driver board, all of the transistors are Silicon, except the DTG110B Final.

If you have another receiver, take an old RCA Cable and add a 0.1uf 400V film cap to the center lead, connect to AUX on the other receiver, and use the cap end as a signal tracer. Work back from the output toward the inputs to see where the signal gets stronger on the weak side. The component directly downstream from the gain should be the bad part.

If you haven't already, clean ALL the control switches, pots, slide switches. Basically if it goes Roundy Round, in/out, up/down gets cleaned. A second or 3rd cleaning may be needed unless you dis-assemble and physically remove the corrosion. Most times (80%) a spritz of DeOxit D-5 and friction (moving the controls 40-50 times) will do the trick. Then finish up with some Faderlube or DeOxit Gold for lubrication.

If you've recapped the whole unit except for the output coupling caps, You're not done yet. Why replace only 6 sparkplugs on a V-8?? or 3 of 4 bald tires? I'd replace them.

Larry
 
Hi Larry, good to hear from you again...

I guess I was unclear,,, I didn't do anything to this guy except, clean the pots and switches, until they were quiet, replaced all the burned out bulbs, disconnected a few sets of PS resistors, to test them, and take some readings...
I mentioned the coupling caps because they seem to be the 1st link to the amp boards, and they look like they will be a bear to access/replace!!! So, Murphys' Law dictates, they have to be changed!!
I basically wanted to see if this amp was worth the effort performance wise, (as compared to the Sansui 800), before ordering a bunch of parts for it... If you think its going to be time well spent, I will start with the coupling caps, as the PS caps are easily accessible...

I asked about V changes in tenths, as SS V is much lower than tube gear, but all the readings I compared so far, are within 10%...

Thanks again for your input,
Regards,
John
 
Most of the 1st gen FISHER's are low power (under 50w rms) with the 220-T about 20wpc RMS (55w ihf). They sound very much like their tube couterparts, but can be finicky at times, especially the Multiplex section.

If the transistors are socketed, you can pull them one at a time and give each socket a drip of DeOxit and slide the transistor pins up and down a few times carefully. This helps some, and in one case (400-T) brought back the mpx for me.

Most of the lytics on the boards are Mallory's encased in Plastic (which I find pretty good and rarely change them unless there is a problem on the board.). REPLACE the Main Filter, the 2 output couplers, The Main diodes, and the rest of the loose power supply caps. Once the power supply is doing what it's supposed to reliably, then fiddle with it in stages.


Actually the coupling caps are the last link to the speakers from the outputs. C73 and C74. 1000uf/50V (IIRC). Flip it upside down. The 3 BIG caps in the Right back corner are left to right C74-C73-C53 (Right output, Left output, Main Filter). Replace those 3 1st. That will most likely clear up a lot of the static. Also replace the 4 diodes on the main cap(CR4) with 1n5404's.

I wouldn't expect a drastic change from the FISHER like you got from the SANSUI. Think of a Sansui as a 71 Chevelle with a Hi output 350 4V, and the FISHER as a 66 Fairlane with a 289 2v. OR Sansui for the younger bunch(rock) and the FISHER for the older crowd (big band in background). I would expect it to clear up and have a tonal quality close to the later FISHER tube receivers, albeit a lower WPC.

Pages from the 1968 FISHER Catalog.

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Thanks Larry,,
That's the info I needed... this isn't an urgent project, but sounds like it should be fun, and not too costly for parts...
I think this little guy could actually sound pretty good, with a little effort....

Regards,
John
 
Thanks for replying,,,
I did try the Mono-Stereo switch, Mono more or less centers the volume level...
.....

Ok, so the problem should be ahead of that. Switch the MONO switch back to STEREO. Next, take a cable and connect the RECDR OUT jacks between left and right channels. This will be the equivalent of a mono switch at that point.

If the levels are now equal, the problem is in the preamp board, selector switch, or input jack wiring.

If the levels are unequal, the problem is in the tone control section.
 
Larry, Thanks for adding the specs,,,
Fred, I will try connecting the recorder out jacks together, and report back...

I missed these two posts, thanks again for the info...

Regards,
John
 
Ok, so the problem should be ahead of that. Switch the MONO switch back to STEREO. Next, take a cable and connect the RECDR OUT jacks between left and right channels. This will be the equivalent of a mono switch at that point.

If the levels are now equal, the problem is in the preamp board, selector switch, or input jack wiring.

If the levels are unequal, the problem is in the tone control section.

I think I got it,,, re-cleaned the Mono-Stereo switch, and selector switch, and the volume level seems the same from both channels...

Only things left,,,, replacing caps, (Kutztown tomorrow, cap guy usually there),, and I noticed teh stereo indicator lamp doesn't come on,,,haven't unsoldered the leads to it to check teh bulb, however, I think Larry mentioned "tricky" MPX sections in these receivers, at times...

I'm usually asking questions most of the time on AK,, so here's a little "quick fix" I made to replace teh panel buss type bulbs...works great...

Got some old series Christmas lights, 6V seem to work OK, and took teh bases off, then drilled a hole in teh center of one of the bases, so it would allow the tip of the bulb to fit in,,, assemble the lamp, with a base on one end, w/one wire sticking thru a hole, and the other wire against teh bulb pointing towards the other socket,,, add an extension to teh 2nd wire, and put it thru a hole in teh 2nd cap, and slide teh cap over teh tip of teh buld, with the wire poked out a wire hole... wrap teh wires around teh plastic caps, and put the bulb back in the amp, aligning so teh wires are held against the amp socket contacts... I put a small drop of super glue on the bulb/socket joint to keep it assembled... I painted teh side of teh bulb, that was facing away from teh dial, as Fisher did...

Thanks again for the help with this amp...

Regards,
John
 
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Well, seems I spoke too soon and made a rookie mistake, I didn't remove the jumper after I cleaned the switches/pots!!
I did however, adjust the stereo separation pot on the pre amp, and was able to center the two channels, with the balance pot also centered... Don't know if its correct procedure, as the SS pot is mostly towards the R channel side,, so maybe there are some differences in components, L to R on the preamp board...

I can hear the difference between stereo and mono, when that switch is used, but the stereo beacon doesn't light up,,, I removed and tested the bulb, and it barely glows at 12V,,, Connected a meter to the beacon wires, and can read 5-6V while tuning FM..

Gaining on it, I think it will sound pretty good with new caps...

Regards,
John
 
I like the idea of sockets for the transistors. FISHER did that for a short time, (less than 2 years it seems) and it looks like only on the 67-68 models. I've got a 550-T, a 700-T, and a TX-100(Int amp) and all have at least some socketed transistors. The only real drawback is the pins and the sockets get dirty and the loss of conductivity is a bit higher. Also if they are jarred fairly hard it's possible one or more could come loose. But checking under the hood before plugging it in isn't too hard or does it take a lot of time.

10'll get you 50 that the bean counters nixed the idea when those models ended their run.
 
I like the idea of sockets for the transistors. FISHER did that for a short time, (less than 2 years it seems) and it looks like only on the 67-68 models. I've got a 550-T, a 700-T, and a TX-100(Int amp) and all have at least some socketed transistors. The only real drawback is the pins and the sockets get dirty and the loss of conductivity is a bit higher. Also if they are jarred fairly hard it's possible one or more could come loose. But checking under the hood before plugging it in isn't too hard or does it take a lot of time.

10'll get you 50 that the bean counters nixed the idea when those models ended their run.

Yep,,,
This amp was dropped or bumped hard enough to dent the rear corner of the aluminum cover, I fixed the dent, and noticed one transistor on an output heat sink was loose,,, I cleaned the contacts and plugged it back in...

I read that this amp is from 1966....

Regards,
John
 
The multiplex lamp's on fisher's usually use a differential to turn them on and off. When in mono you have the same voltage on both ends of the lamp so no light. When in STEREO, the one end from the MPX board either drops or raises, and the difference is enough to light the lamp. One side should be from the POWER SUPPLY and the other from the MPX board. (I'll have to pull the scat to see what's what).

Larry
 
Ok. Quicky look at the 220-T scat indicates the lamp is fed from the
POWER SUPPLY +15V B+ on one side and PIN 4C on the other. There is a 2n2924 (Q404) and a 1uf cap (C411) that are supposed to be connected to the PIN 4c. With it in MONO Take a voltage test on Pprobably IN 4c and again in STEREO. Disconnect the Lamp from the pin and isolate so it doesn't short o nthe chassis.

The Schematic and the board drawings DO NOT AGREE! You'll need to track the trace on the board from 4C and list the component and which pin it connects to. Test Q404 (using the 6 way test from Echowars and Mark the Fixer's post #11 here.... LINK .....see post #11. If bad, Replace with 2n2924 (mouser has them). Also replace the 1uf cap. You can probably use a 50V(check cap voltage 1st) ECQ Film cap here.
 
Thanks Larry,,
I'll try to do teh tests,,, and get back to you...
Not impressed with teh Fisher schem,,, not enough info, and no breakdown on the preamp board...

Regards,
John
 
.....
10'll get you 50 that the bean counters nixed the idea when those models ended their run.

Actually, it was a carryover from tubes. Did you know that early transistors were actually sold individually boxed like tubes? I had some from RCA.

Today, the sockets cost way more than the transistors (or chips) and with a good solder sucker, I can have a 14 pin chip out just about as fast desoldering as trying to pry it out of a socket.
 
First, we need to deal with one problem at a time and the unbalance problem should be resolved before looking at the multiplex decoder.

The separation control on the preamp board is only connected when the selector is in the FM position. The FM position connects preamp terminals 1J and 1M. Otherwise, the separation pot is only connected at one end and does nothing. It is used to fine tune the separation after the MPX is aligned.

If the multiplex decoder is separating channels (even though the stereo lamp may be out), the balance issue will be hard to trace. To check the level unbalance problem, a true mono source is needed.

Try the AM function which feeds the tuner to both channels and connects them at the selector switch. This will ensure that the exact same signal is fed to both channels. If it is still unbalanced, then the original problem still exists and if it is balanced with the jumper cable at the RCDR OUT jacks, then the problem is ahead of that.

The transistor (Q404) on the MPX board is only a sink and there will be no voltage at pin 4C if the lamp is bad or disconnected. If you have not verified the condition of the actual lamp, you can use a 1K resistor in series with an LED (correct polarity of course) between pin 4C and +15V (across the existing lamp). The MONO-STEREO switch must be in STEREO as there is a second pole that disables the MPX, turning off the light. Or, you can use the 1K resistor without the LED and measure the voltage.

Unless there is an obvious problem, you will probably need an oscilloscope to deal with the multiplex. We should be able to deal with it using stations and not need a stereo generator.

Larry, where do you see a difference between the MPX schematic and board view? Pin 4C connects to a jumper at Z402, then C411, then Q404 collector, then pin 11 of a circuit pack. I'm looking at a manual starting at s/n 10001
 
Fred; I see what you are saying on the board layout, but not the line schematic. 4C connects to the collector of Q404 and C411 then to pin 11 of the PEC and then C411 other side and the base of Q404 go to Pin 9 of the PEC. Pin 11 then branches off thru different pins to other areas of the tuner. Same with Pin 9. Nowhere do i see a direct connection to the Jumper on pins 4 and 6 on Z402 except on the actual board drawing. It's cornfusing as hell! Same with the Jumper on Z401 for Pins 5-6!
I'm looking at the same manual.

Larry
 
The multiplex board is the same as that used on the 440T except that R410 is replaced with a different value and called R411. The jumpers are there as well. For some reason, they just don't show them on the line schematic. They are shown at the coils but with nothing connected. Back when this stuff was designed, the boards were probably laid out by hand and the jumpers probably ended up being easier than a revised board layout. Been there, done that, with my hand designed, wired on the back, boards where I eventually give up trying to rearrange stuff and just eat the fact that I'll need a jumper or two.

Are the jumpers separate from the coils on the board or could they be an integral part of the coil but not connected to anything internally?
 
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