60 MB restoration - Printable Version

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+--- Thread: 60 MB restoration (/showthread.php?tid=6431)

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RE: 60 MB restoration - Bob Andersen - 10-29-2013

Not yet, but I will and you'll see I ran into a number of problems.

One, the output attenuator isn't working on my 3336A. Luckily, it's stuck on a level that was OK for this project, but I'm going to have to do something about it.

Two, the z-axis input on my HP 54600B scope only does trace blanking - not intensity modulation. So I had to dust off my old 465 scope.

I'm also a little disappointed that the 3336A doesn't support FM modulation, but the AM modulation does work very well.

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RE: 60 MB restoration - Bob Andersen - 10-30-2013

Spent tonight repairing a pair of speakers.

Here's the one that came with the 60MB. It had been re-coned ages ago and the glue failed on both he surround and spider. It still sounded OK until the volume was really cranked up when it would started buzzing badly. I spread some Aleene's clear gel tacky glue around and will let it set up over night.
[Image: http://farm8.staticflickr.com/7396/10568607704_3d287f7298_c.jpg]

[Image: http://farm4.staticflickr.com/3700/10568810513_859030ff17_c.jpg]

I also tackled the speaker that came with the parts chassis. The cone was completely trashed and the spider damaged but useable I think.
[Image: http://farm4.staticflickr.com/3831/10568599874_677c2978fc_c.jpg]

I cleaned off the glue residue with Acetone and used a little Naval jelly on the frame. Some Boeshield T-9 should keep the rust at bay.
[Image: http://farm3.staticflickr.com/2876/10568601324_5feba5c8c6_c.jpg]

The new cone came from MAT Electronics. I just had to trim about 1/16" around the rim and slightly enlarge the VC hole. The foam surround does stick up a bit beyond the frame edge so I'll probably have to use some shims
[Image: http://farm8.staticflickr.com/7383/10568551706_ff69a4900a_c.jpg]

I'll fire them up again tomorrow and use whichever sounds better in this set.
[Image: http://farm6.staticflickr.com/5532/10568604914_618697c744_c.jpg]

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RE: 60 MB restoration - Bob Andersen - 11-01-2013

Although my re-coned speaker works OK, at higher volume levels that damaged old spider starts to vibrate. The other speaker is working great now that the surround and spider have been glued back down so that's what I'll stick with.

Tonight I moved on to wiring in a reproduction cloth covered power cord. I'd heard about the "Underwriter's Knot" before, but this is the first time I've used it. It's easy to tie and really does provide a great strain relief. I also added a bit of heatshrink tubing over where the outer cloth covering ens to prevent it from fraying.
[Image: http://farm4.staticflickr.com/3827/10603195045_98bc057bf8_c.jpg]

I also found a nice spot to mount a fuse holder using ad existing chassis hole.
[Image: http://farm6.staticflickr.com/5519/10603450583_3f53f97436_c.jpg]

So what do you guys use for chassis bolts ? An original is on he far left. The closest modern version I could find is the sheet metal screw next to it. The tread pitch is right, but it'snot quite as snug a fit as the original. The other two bolts are the right diameter but he prong pitch.
[Image: http://farm8.staticflickr.com/7332/10603449713_9633400dd9_c.jpg]

Argh! I know I have a spare pair somewhere but can't find them
[Image: http://farm8.staticflickr.com/7386/10603211114_e1a7c93645_c.jpg]

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RE: 60 MB restoration - Arran - 11-01-2013

You need to find a place that sells nothing but fasteners, they might have something closer then that sheet metal screw. The only other option is to break out a tap and die set and modify the holes to accept machine screws. One of the old radio parts venders supposedly sells replacement chassis screws for Philcos but I have a feeling that they are just sheet metal screws like the second ones you have.
Regards
Arran

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RE: 60 MB restoration - Bob Andersen - 11-01-2013

I'm calling it doe for now If I ever come across more suitable grille cloth, I'll replace the old tattered original.
[Image: http://farm6.staticflickr.com/5533/10610622784_567a745953_b.jpg]

[Image: http://farm4.staticflickr.com/3787/10610860333_4a6cc3f682_c.jpg]

I think it's a big improvement over what I started with
[Image: http://farm9.staticflickr.com/8385/8614742266_e39644fcf6_b.jpg]

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RE: 60 MB restoration - w4rtc - 11-01-2013

Looks good Bob, as always

Joe

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