Fisher X-202 Rebuild

[audiodon]

Interesting about the cold solder joint. I hadn't considered that. When I've had a problem like the OP mentioned with an intermittent channel, I've found:
1. Tube pin bent over so far it sometimes contacts the chassis
2. I hit a nearby wire when soldering, melting the plastic, and that exposed wire shorted against something
3. Something shorted under the chassis to one of the wires either to or from that tube position
4. Tube pins needed retensioning.

Now I can add cold solder joint to that experience.

 

[walyfd]

There was a cold joint in my RCA that would make all sorts of trouble when it heated up.

As for the red indicator light, I swapped the old bulb with a new one last night. It glows at maybe 30-40% of full power and is barely visible even in a dark room. The Channel A and B lights overpower it. The original bulb was still faintly on but not enough to see with the cover on.

Here's the best I could make out what that lamp tag says:

Channel Indicator Lights

The five colored jewels provide a visual indication of the type of service for which the X202 is set, and will light in different combinations depending on the position of the Mono-Stereo switch. The red jewel (C) serves as a main On-Off pilot light as well as a Center Channel indicator. It brightens when the Center Channel Switch is turned on. The table below is a guide to the different light sequences. For example, with the Mono-Stereo switch in STEREO position, the (illegible) Jewels (A and B) will light, indicating that the signal at the A and B inputs will be heard on the A and B (left and right) speakers, respectively.


The Executive V Owner's Manual mentions the red light will come on when powered on but doesn't say anything regarding intensity. The lamp guide in the manual shows it as "off" unless the Center Channel switch is "on".

 

[dcgillespie]

The illegible word on the tag is "outside".

Dave

 

[walyfd]

Either you have a clearer example of the tag than I or your eyes are a lot better than mine! Thanks!

 

[2dbit]

Thanks for the info regarding the center channel light illuminating. I feel a lot better knowing that it's normal!

As for the popping, I opened the unit back up and found that tapping on no one component causes the pop, but on the terminal strip seen on the left hand side here:

Tapping anywhere on the strip causes the sound. Equally tapping on any component attached to the strip will cause it as well, likely vibrating to the strip.

I didn't have much time to mess with it, but I wonder if there's a poor bond between the tab and the chassis... I'll reflow all joints to ensure that there are no cold solders, but they all look good.

 

[dcgillespie]

It could be any terminal lug on that strip, or don't forget, it could also be at the other connection point that any component connected to that strip is connected to: Moving the strip causes the components connected to it to move, potentially disturbing the connections for the other leads of those components.

Let us know what you find!

Dave

 

[larryderouin]

You probably taken care of them already,,,,,but these look hinky to me. Check the other end of the resistor under the ON/OFF switch (marked with ?).

 

[2dbit]

Sorry, I didn't take a recent picture of that area, (as indicated by the completely missing can cap) All regions look a lot better than seen in that picture following the completion of that area!

Regardless, I went in and did some isolation. No solder joints appeared to be cold, but I went ahead and fluxed and reflowed them all for good measure. I also went and fluxed and reflowed all joints at the opposite end of any component connected to that strip. That did not take care of the problem. I found that if I pressed from the left on the terminal strip it would cause the channel to come back to life.

I had measured 0.2ohms from terminal strip to ground, but suspected that perhaps when there was no load from the multimeter lead, it was a poor connection. I put a small bridge of solder from the ground tab to the chassis. That didn't fix it either.

What I did find was shocking, and disappointing to me. Despite through inspection and resinspection of all components, joints, etc, prior to power application. I missed a short. It's in a highly concentrated area, so I practically had to put my head inside the amplifier and look sideways to spot it. R93 was sitting a bit low and one of its leads had shorted to a terminal lug. A rogue lead that hadn't been trimmed at the same terminal that R97 connects to.

Removal of the rogue lead fixed the problem, and channel B is alive and well.

Here's a pic of where the short was occuring...

 

[dcgillespie]

Congrats on finding the problem! That likely did not do any component damage, other than to your own personal satisfaction of your work -- which is still quite stiller!

What's best to know however, is that you did in fact find and correct the problem, and now the unit can reward you with many, many years of continued enjoyment.

Dave

 

[larryderouin]

HOT DOG! Damn fine detective work. I know what you went thru on this one. I worked on one a couple years ago and could never find a problem (Buzz/humm) in that same area. had the unit a little over a year and never found the problem. Hopefully Naptown has found someone who can find it or has found it. I've been working off and on with my dad on the boat on a Hammarlund SP-600-J and the X202 is a dream compared to that! WHAT A MESS!! My hat's off to the HAM's who restore these.

 

[bhamham]

HOT DOG! Damn fine detective work.

I agree! :thmbsp:

 

[NoTransistors]

I have been following this thread, and you have done some wonderful work, to be certain.
We are all very proud of our fellow member.
My X-202-B needs a rebuild, but I will do nothing more than replace the upright caps and the coupling caps, and install the safety resistors. To go further than that would chance ruining a valuable amplifier.

 

[2dbit]

First, thanks for the props, I'll admit, despite placing all components where they were originally to try and ensure trouble free operation when complete, when dealing with this many new components, I was quite nervous to what I'd hear when I hooked up speakers for the first time!

The ultimate payoff to all the work, is that I can (with no signal input) turn the volume up as far as it can go, and hear no hum, nor hiss. Perfectly whisper quite operation. With my speakers connected, the sound is amazing. I've had the amplifier set in my dining room, and have enjoyed listening to it every day during and after dinner. I suppose I can tell my parents that the amplifier is undergoing test and adjustment for only so long!!!

So far, I've logged at least 20 hours of operation, and have done at least 5 checks to bias and balance. I have maybe done 3 adjustments, these past two times I've checked bias and balance they have been spot-on.

It has bothered me quite a bit that the channel A bulb is burned out. I seriously don't see any justification in spending $14 for a NOS light bulb. I suppose there are people out there who would.

However, I wanted to reach out to this community to see if anyone knows if this bulb fulfills the spec requirements that the originals did:

http://www.grainger.com/product/GE-LIGHTING-Miniature-Lamp-6VC38

Seems to be the same as the originals...

 

[dcgillespie]

The original bulb was in fact a #47 bulb.

Dave

 

[2dbit]

Yeah, I don't doubt for a second that this is a complete set of original bulbs. Growing up, as long as I can remember, the Channel A bulb was burned out. I never knew what any of the lights meant. All I knew is that the middle one glowed dimly, the one all the way to the right was bright, and if I rotated the wrong knob, more/different lights turned on. I never knew what any of it meant, but then again, what kid does...or cares?

So long as the Grainger GE47 bulb meets original specs, I may relamp the entire array so that the amp can have a fresh start on that 3,000hr life span.

 

[larryderouin]

Most Auto Parts Stores will carry #47 bulbs as does Radioshack.

 

[2dbit]

I went ahead and replaced all the bulbs in the array. (though the others were working, the glass had turned smokey colored with age)

It's amazing the difference this has made. Now all those gems shine so bright and vibrant!

 

[2dbit]

Yesterday was my last day with the unit. Having operated the stereo daily for hours on end listening to mostly Disney music with my daughters (I think they're going to miss the amplifier as much as me), prior to shutting down, I've checked bias and balance. I haven't made any adjustments in a few weeks. I believe at this point break-in is complete.

I have returned the amplifier to its home at my family's house. I connected everything and fired it up. My dad grinned quite a bit to see it alive and well.

The first sounds to be played came from the Tuner, a Pioneer TX-6500 II.

I was slightly mortified. The sound that came out was quite lacking. Sounded a bit muddy, and not much bass. I immediately started going through what could possibly have gone wrong. I have the speakers connected to the 16 ohm terminals...They're the original speakers, large wooden cabinets with I believe 10-12" speakers, as old as the unit itself. I moved the balance from left to right. I found that the sound coming from one side sounded normal, bass and treble present (though not nearly as clear as produced from modern speakers), but from the other channel, nothing but mids and highs.

I switched the input over to my iphone. WHEW! The sound that was produced was equal. Left and Right. Though, the sound is still a bit on the muddy side, I suppose this is quite expected when I'm sure the speakers have degraded significantly with age.

I was a bit short on time, so I haven't had a chance to play anything on the turn table.

I suppose the next project will be that Pioneer tuner. A few dried out caps?

 

[larryderouin]

Did you plug both into the same input? If not, it could be dirty contacts on the interconnects, or the RCA's, or it could be the TX-6500 has dirty contacts. Swap the IPhone and the TX-6500 inputs and try it again. If the IPhone now sound's like crap (what apple product doesn't?) it's the 202. You can try the TX-6500 in any input except PHONO.

 

[2dbit]

Hahaha, hating on Apple

I had actually used the tuner input earlier while still at my house. I'll have to swap the leads the next time I'm over to see if the fault follows. That should isolate if the problem exists with the tuner.