Fisher 800C Tuner Alignment AM and FM

[backmd]

Triplett hooked up to TP3 and the input goes to tube shield V2 which is electrically taped to isolate it from the chassis and measures infinity. Chassis on its side supported by 4 business cards on the transformer and wired to shelf with wire. Volume control sprayed with Deoxit D5 and cycled 100 times. Sencore SG165 is hooked up to the tube shield V2.


Z2 top from 19 to 19.5 smoothly after warmup altered slightly to 19.1 buy since bottom is inside tuner cage must remove tuner cage to proceed. Sencore SG165 works well. Peaked bottom of V2 nicely, uses hex


Z3 peaked nicely from top and bottom. Uses hex


Z5 peaked nicely from top but locked on bottom. Uses slot not hex


Z6 peaked nicely from top and bottom. Uses hex

Z7 peaked nicely from top and bottom. Uses hex up to –33.2 volts now! Replace tuner cage on bottom.

 

[gadget73]

usually not a bad idea to turn the generator level down as the voltage climbs, otherwise the limiter will start doing it's thing and the peaks get much less defined.

anyway that much of a change in ALC voltage is a good hint it was pretty far off. If you go back through and do a visual alignment now it should just be a touch-up sort of thing rather than having to really fight with it.

 

[backmd]

usually not a bad idea to turn the generator level down as the voltage climbs, otherwise the limiter will start doing it's thing and the peaks get much less defined.

anyway that much of a change in ALC voltage is a good hint it was pretty far off. If you go back through and do a visual alignment now it should just be a touch-up sort of thing rather than having to really fight with it.

The 6HR6 tube should be here tomorrow. Can you believe with the bad 6HR6 I get higher signal strength than with the new 6AU6? The new 6AU6 is supposed to be just as good. But that is not true with my particular Fisher 800c at the V3 position. Tried it with two different 6AU6 tubes. The alignment was done with the bad 6HR6 tube.

 

[gadget73]

6hr6 has different cutoff characteristics, so I'm not surprised it works better than the 6au6 in a circuit designed for a 6hr6.

 

[dcgillespie]

In typical use the 6AU6 is a good substitution, but strictly speaking, the 6HR6 produces nearly double the Gm of a 6AU6, so it is ultimately capable of better performance. But again with typical use and a healthy IF Strip, the loss of performance using a 6AU6 will be quite minimal.

Dave

 

[backmd]

Initial turn on WFMT is 2.8 and in clear stereo! I have a hex alignment tool at Z2 top! A minute later we are at 2.5 and the top of Z2 is aligned. Five minutes later we are down to 2.3 and the top of Z2 is realigned. Bottom of Z2 brings us back to 2.7, very good! Z3 top and bottom aligned and we have 2.75 or so! Z5 adjusted top and bottom. Unable to fabricate a good slot tool from chopstick. Z6 peaked top and bottom. Z7 peaked top and bottom with the Sennheiser ATH AD700 headphones listening for the best stereo imaging and soundstage, sounds really really spooky good!


The big 3 are in stereo ranging from 2.7 to 3 on the signal meter. I now get –34.3 volts at TP3 after adjusting L1 at 90.1.

Many Many thanks to Dave at DCGillespie, gadget73. and LarryDerouin!

 

[larryderouin]

Yeah, after 8 years my 800c Executive FM multiplex has gone wonky and has trouble staying locked on a station
I cannot do multiplex repairs

Not that there is much to listen to on FM anymore

seems to be a problem with ALL my tube receivers

Best of luck with your 800c

Don; FISHER aligned the MPX separately. If he's still doing them, Dave can align the MPX as long as it has good tubes with it. He's got a cool little jig to power it up and the FISHER 300 MPX Alignment generator. Check with him. All you'd have to do is pull it out of the 800c and ship it to him.

Larry

 

[backmd]

Are these a hex core transformer ? If so, most of the time you can push the alignment tool through the upper core into the lower to make the adjustments rather than flipping the unit over.

if not, just stand it up on its side.


using the signal meter is just monitoring the ALC circuit, which is what the eye tube should be doing in mono mode. Basically you're peaking it for strongest response, which may not always give ideal performance. With FM you're more interested in a symmetrical response than the strongest peak. Symmetry gives lower distortion and widest frequency response.

I have the Velleman High Frequency Adjuster set with 10 pcs. Of significant note, the narrowest part of the tool is the hex part. The next wider part is the circular part that is not slotted but a larger diameter. Maybe there are tools where the hex part is a larger diameter, and if so, that would be great, then I could turn the lower core without flipping the unit over.

 

[jvstratman]

GC Electronics 18-530 CB Radio Alignment Tool Kit?

 

[gadget73]

Not sure which kit has what honestly. The set I have has a stem where the hex is larger but I have no idea who made it.

 

[backmd]

Not sure which kit has what honestly. The set I have has a stem where the hex is larger but I have no idea who made it.

The GC8282 is the wonderful alignment tool where the end is fatter than the middle piece so it may be able to do an alignment without flipping the unit over to access the bottom slug. I have yet to try it but apparently you can adjust the upper and lower slugs from above. It comes with the GC Electronics 18-530 CB Radio Alignment tool kit.

 

[gadget73]

I've got pieces from assorted places. I did buy a kit at one point but I don't remember which one. All my alignment doodads live in a cigar box and its a mix of whatever was in the kit, some old Radio Shack things, and stuff I've ended up with over the years from assorted places. One I actually find myself using often is home made. Its a fiberglass rod with a #10 screw run into it, cut off, and ground to a flat so it fits into trimmers or other slotted adjustments. Others obviously started life as one thing and were shaved into a different shape for whatever purpose.

 

[backmd]

The GC8282 is the wonderful alignment tool where the end is fatter than the middle piece so it may be able to do an alignment without flipping the unit over to access the bottom slug. I have yet to try it but apparently you can adjust the upper and lower slugs from above. It comes with the GC Electronics 18-530 CB Radio Alignment tool kit.

There is a seller on the usual auction site that is selling just the GC8282! I think that is a real bargain, since this is a critical alignment tool to engage the upper and lower slugs so one does not have to flip the unit except for Z5 where there are standard screwdriver slots. More specifically:
Transformer Upper Lower Notes
Z2 Done Done Unremarkable

Z3 Done Done Unremarkable

Z5 Done Done Both are standard slots!

Z6 Done unable There is no lower slug

Z7 Done Done Unremarkable

 

[backmd]

There is a seller on the usual auction site that is selling just the GC8282! I think that is a real bargain, since this is a critical alignment tool to engage the upper and lower slugs so one does not have to flip the unit except for Z5 where there are standard screwdriver slots. More specifically:
Transformer Upper Lower Notes
Z2 Done Done Unremarkable

Z3 Done Done Unremarkable

Z5 Done Done Both are standard slots!

Z6 Done unable There is no lower slug

Z7 Done Done Unremarkable

Hopefully this will help someone. Ideally we all stand on the shoulders of our wonderful teachers!

 

[backmd]

There is a seller on the usual auction site that is selling just the GC8282! I think that is a real bargain, since this is a critical alignment tool to engage the upper and lower slugs so one does not have to flip the unit except for Z5 where there are standard screwdriver slots. More specifically:
Transformer Upper Lower Notes
Z2 Done Done Unremarkable

Z3 Done Done Unremarkable

Z5 Done Done Both are standard slots!

Z6 Done unable There is no lower slug

Z7 Done Done Unremarkable

As encouraged did a visual alignment with the Sencore SG165, while measuring voltages at TP3 with the RCA Senior Voltohmyst. The voltage peaked at 66 volts negative at TP3. It seems just a hair better on the classical station, maybe just a wee bit more depth. I could not resolve the adjustments unless they were at the R or L edges of the 10.7Mhz flat line. So I went back and forth and set it midpoint between the R and L sides of the flat top. Will put it back in the "rack" and hookup to the Infinity Intermezzo 2.6P and KEF LS50.