Magic Eye solution for 500B

[Sam08861]

Just replaced the original magic eye tube (orenz EM84A) with a NOS (new old stock) $5 tube from ebay and all I have to say is WOW!

The tube is a Beijing Shuguang 6E2 and I got two shipped (from Hong Kong) for $10 total, so also have the comfort of a spare at the ready for the future. There's several sellers on ebay so not endorsing anyone in particular but you can PM me if you want the seller I bought from if you want. Also glad to post pics if anyone wants and it took 6 days to arrive to my mailbox from the time of order.

It is about, I don't know, 100x brighter, lol. Used to be the 'stereo beam' letters were the bright item, now the magic eye is by far the brightest thing on the dial. It's so bright that it makes the background of the dial much blacker and also seems to be backlighting the dial markings and letters a bit, when previously the light bleed from the sides were a bit noticeable, particularly when there were ANY smudges on either side of the glass. This is no longer a problem and the color has a very 'bioluminescent' vibe.

The blue green color nicely matches the 'Fisher' text and dial markings. The two beams close up to about a hair's width on strong stations and the edges are very crisp. With the brightness and crisp square ends, the tiny gap (about the width of a toothbrush bristle) is still visible from 2-3 feet and gives a very 'precision made' look when it's 'full power.'

If anyone has a weak magic eye indicator, I highly recommend these 6E2 tubes as they truly a plug and play 30 second upgrade. Very happy and way too over-excited with this low cost purchase.

(Guest for me, it's the little things as I wasn't nearly this excited about scoring a Shure V15III cartridge for next to nothing or even plugging in a 'McShane' matched quad, lol. Guess it's the 'cool' factor, lol.)

 

[Sam08861]

Some other observations. This lighted part tube is a about 1/8" longer than the original on each end, so on weak signal strength, the short ends of the beams are sometimes not visible through the slot in the plastic shroud in front of it.

While the tube is not as good as the original in the regard, on my unit, this seems to be more of a problem in Stereo and not in Mono, and I have a 'dancing beam on most stations and sometimes the mono vs stereo beam sizes 'don't agree,' meaning the peak points are at different broadcast frequencies. I've read this type of behaviour (excluding tube length) may be an alignment issue, but if not, the amount the eyes close can be adjusted by varying a particular resistor. Had this same behaviour with the old tube also, so not caused by the 6E2.

 

[gadget73]

The closing of the eye in mono vs stereo is possibly alignment. The eye is fed from two different sources in these, in mono mode it runs off the AVC line and reads peak signal strength and in stereo mode it runs out of the MPX unit and indicates the strength of the pilot tone. Those two points don't necessarily land at the same point, though it should be very close.

 

[dcgillespie]

For most MPX stereo stations, the agreement of FM carrier signal strength (as functions in Mono mode), and the pilot signal strength should in fact show close agreement. If they are consistently off on all stations to a notable degree, then it indicates a misalignment between the tuner section and the MPX section, the fault of which could lie in the tuner section, MPX section, or both. Either way, an alignment would be required to correct it.

Dave

 

[Sam08861]

Thanks Dave, gadget,

From the service manaul, the process appears straightforward needing a vtvm, signal generator, variable power source, insulated tuning 'rods' and an oscilloscope. However, I've read on this forum that aligning a Fisher isn't something a novice should perform and to do this properly, there is other knowledge, experience and equipment needed. If that's not totally true, I'd love to learn how to do this. i.e. what is require beyond the service manual instructions. There is an antique radio swap meet this weekend near me this weekend (NJARC), so perhaps that's an opportunity to get some hands on advice from the club members.

That said, I do seriously heed the warnings from the experts on this forum... Any suggestions in the NY/NJ/Easter PA area for a tech with the right equipment and knowhow? Would I just ask for an 'FM alignment?'

Any local experts/servicers, please feel free to PM me if that's allowed.

 

[gadget73]

You really want a sweep generator and an MPX generator to do a proper alignment. I've done the VTVM and twiddle stick method on things, and it can improve things that are hopelessly messed up but it usually doesn't give the best result overall. Usually thats where I start on things where people have been inside "adjusting" things already. Beyond that point I sort of tweak it a bit by ear if it sounds messed up. Unfortunately I don't have the gear to do it properly beyond that point so I try to keep my mitts out of tuners whenever possible.

 

[Sam08861]

Thanks Gadget,

I'm leaning toward a tech doing this right now.

If I do have an Eico 369 sweep generator that I rehabbed some time back, and a new 10.7 MC crystal so wondering if that would fit the bill if I were to ever try this in the future.

 

[dcgillespie]

That will do a good job of certainly the IF strip, but it won't do the multiplex section. However, the Eico manual will probably instruct an alignment method based on stagger tuning the IF transformers. You should disregard those instructions and use the published Fisher instructions for alignment, as the IF transformers in your unit were not based on stagger tuning to achieve a flat band pass response.

Dave