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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Fri 15, 2019 3:53 pm 
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metzman wrote:
I've found that beach radios are prone to getting grit under the voice coil cover and reak havek with buzzing and distortion. It's a tedious fix but been successful at cutting out that portion of the cone to remove sand and free up the coil then gluing it back in place.

I can't resist this one. How could sand cause buzz in speaker?

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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Fri 15, 2019 5:37 pm 
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Hey Tom,

The sound from the speaker as the voice-coil rubs on rough surface does sound "buzzy"---think that's what he means.

Metzman---Since this issue is caused by corroded surface of magnet due to salt water exposure and not just the sand, the outer surface of magnet would need to be cleaned & polished to remove the friction. More than what I'd want to attempt as speaker could be destroyed in the process...

John


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Fri 15, 2019 9:01 pm 
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xrhonda91 wrote:
More than what I'd want to attempt as speaker could be destroyed in the process...


Exactly. I think everyone who has worked on half century plus electronic components recognizes their frailty, and what limitations should be exercised in attempting to refurb them.

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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Fri 15, 2019 9:11 pm 
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Location: Mesquite NV 89027 (from Coventry, UK)
That is a sharp looking radio. I hope that you manage to sort out the remaining issues.


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 2:42 am 
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Quote:
Exactly. I think everyone who has worked on half century plus electronic
Quote:
recognizes their frailty, and what limitations should be exercised in attempting to refurb them.


The speaker doesn't work anyway so there's nothing to lose in trying to fix it. It looks like he already removed the dust cover. The next step would be to separate the cone from the coil and pull it out of the cavity. Desolve the corrosion clean it thoroughly and reassemble. The groove is too narrow for a knife blade because of the curvature, so it needs to be scraped out with a metal guitar string (D string works the best) A tedious process but not an impossible feat by any means. It takes time and patience but to be honest this guy seems to always be in a rush to get projects done so he probably wouldn't be able to do it.


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 6:34 am 
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metzman wrote:
Quote:
It takes time and patience but to be honest this guy seems to always be in a rush to get projects done so he probably wouldn't be able to do it.

I don’t think that is a fair assessment of John. Just my opinion, but having followed many of his projects I can say that he will spend hours to get something right. However, there sometimes comes a point where one has to decide that the project may not have the desired outcome, and is better left alone. As I said, just my opinion.


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 7:51 am 
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Colin Ames wrote:
metzman wrote:
Quote:
It takes time and patience but to be honest this guy seems to always be in a rush to get projects done so he probably wouldn't be able to do it.

I don’t think that is a fair assessment of John. Just my opinion, but having followed many of his projects I can say that he will spend hours to get something right. However, there sometimes comes a point where one has to decide that the project may not have the desired outcome, and is better left alone. As I said, just my opinion.

I'll go farther than Colin; I would say that the last thing John is in, is in a rush. IDK where you get that from.

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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 1:37 pm 
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Following a restoration project in a thread can be misleading as it doesn't convey the hours spent behind a series of step by step photos. I am often amazed at the time and effort John puts in to bringing a radio back to life that I would have passed over as hopeless.

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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 4:05 pm 
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Colin Ames wrote:
metzman wrote:
Quote:
It takes time and patience but to be honest this guy seems to always be in a rush to get projects done so he probably wouldn't be able to do it.

I don’t think that is a fair assessment of John. Just my opinion, but having followed many of his projects I can say that he will spend hours to get something right. However, there sometimes comes a point where one has to decide that the project may not have the desired outcome, and is better left alone. As I said, just my opinion.

Agreed, besides John sort of agreed that sand maybe could cause a buzz in speaker. I'm still not in agreement with that. My definition of a gritty, scraping sound doesn't translate to buzz.

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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 4:31 pm 
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Having studied psychiatry for years I'm very aware how obsessive-compulsive minds work. He admitted he couldn't do it and that's perfectly fine. Most wouldn't attempt such an endeavor. I'm the type of nut that would. It would take the same kind of dedication as hand unwinding a power transformer counting and recording the number of turns then hand rewinding it again with new wire. I'm not bragging but I've done it successfully. I could have just found a replacement but instead took the long hard road for the challenge. It took about 6 weeks. The total radio project took 9 months. You just can't be worried about having a working unit in any given time. It takes as long as it takes.


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 4:45 pm 
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Quote:
Agreed, besides John sort of agreed that sand maybe could cause a buzz in speaker. I'm still not in agreement with that. My definition of a gritty, scraping sound doesn't translate to buzz.



When tiny particles get trapped in the cavity in which the voice coil rides they bounce against the paper cylinder of the coil as it vibrates causing buzz. That's the mechanics of it. But looking at his coil it looks like corrosion is inhibiting its movement so buzz is probably not a factor in this case.


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 4:51 pm 
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Hopefully there's a chance that just giving the solar array an extended sun bath may rejuvenate its operation.


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 6:54 pm 
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First of all, thanks very much to all who came to my defense---that in itself meant a lot !

Continually try very hard to avoid getting too "personal" anyplace public, but am a very analytical person in all that I do and how I live and attempt to carefully listen to (or read) what others say and try to understand based on past communication and what little I know about their character. One of the main reasons for my being here on ARF along with interest in radios is that there are many good, decent, helpful people... Have known others through the years who try to motivate by saying that "you can't do it", and when younger was offended by that statement, but later understood---that's how I took the statement after initial shock... And yes, I do try to complete projects as quickly as possible while striving to do as thorough and good of a job as possible. Have never liked unfinished work of any kind "hanging over my head" or cluttering up "space", but have spent long hours, days, or more on radios once the needed materials and motivation were present... It's a "diversion" from some of the sorrows & worries due to family issues and the "craziness" of this present culture. Won't even mention the car, truck, and house/garage projects that I've worked on nearly every spare moment until completion through the years...

Since this is a historic radio, did not want to risk destroying speaker as another may never be found---at least for what I'd want to spend... Did consider his suggestion and could probably do it, but the corrosion may have roughened the outer surface of the magnet so much that cleaning wouldn't cure problem. Also noticed that the voice-coil form was very brittle and started to crack while working with it, so another reason to leave it alone... Try to analyze all the possible outcomes to see if chance of success outweighs failure... May try to find a replacement that fits so radio can be used, but want this one intact for "future owner" since it does work to some degree...

Am planning to attempt disassembly of solar panel this weekend if utility knife is sharp enough to cleanly cut through glue on back cover. Have isolated the area of poor connection by tapping on panel during period of proper operation and think it's a bad solder joint at one of the silicon elements.

Thanks again & stay tuned !
John


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 6:59 pm 
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And don't rush it! :wink:

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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 7:08 pm 
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John,

As always, I enjoy your meticulous approach and all the great documentation. Your work is top drawer!

In my opinion, the free psychoanalysis that you received in this thread seemed a little bizzare, but I'm sure intentions were good.

Tim


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Sat 16, 2019 8:45 pm 
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Location: Palos Verdes, CA
I guess I'm a lot like John in that I like to finish working on a vintage transistor radio project once I start. As my skill level is quite limited, I usually start with a transistor radio that I didn't pay much to acquire, so if I mess up, oh well! At least I'll end up with some more parts! - Mark


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Mon 18, 2019 5:30 am 
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Location: Indianapolis, IN
Thanks Guys !

Solar-panel "open-heart surgery" today !

Was planning to cut through glue around edge of solar-panel bottom cover insert and after careful inspection under magnifier saw that glue had wicked between it and top which killed this idea...

So again closely inspected the interconnections between silicon elements and noticed what appeared to be corrosion residue beneath one. Attached output of panel to meter. applied light, and began tapping and pressing until normal output indicated---still erratic, though... Then pressed firmly, but carefully top & bottom over each element until one showed somewhat consistent reaction---and it was the one with the residue !

Carefully measured and marked location of connection on panel bottom and very gently drilled into plastic using fingers with bit until point just penetrated---then used small flat-blade screwdriver , again very carefully, to "bore" through to black foam support. Removed debris with "trusty-hatpin" and vacuum cleaner. The support foam had deteriorated into a gooey black mess which took some time to remove without causing damage. After all of this, found that the connection beneath element with the residue was perfectly good ! But now could measure output to this point and found that the open was on the top side of this same element---fortunately ! Looked very closely with another magnifying glass along with ring-lite magnifier and could now see that the wire was fractured right at the solder connection and was only touching the edge ! Whew !

Measured location of this fault and again drilled hole using process above---once crud removed, verified other electrical "leg" of array to this point and all was good---again, very grateful ! Since failed connection was on top this time, the element had to be removed for access which required "surgery". Held panel up to bright light to see outline of silicon through foam and marked outline with Sharpie, then slowly and very carefully melted through plastic cover with tip of soldering iron. Removed this segment of plastic and cleaned up inside of "incision" so that element would come out. Had to desolder the good interconnecting wire on bottom and bent it out of the way. Folded over a small piece of masking tape and stuck it on back of element to pull through opening. Thoroughly cleaned both sides of silicon with Q-tips and Isopropyl alcohol. Wanted to use the best wire possible to replace corroded piece and decided to use a strand from some scrap high-quality Teflon wire. Carefully soldered strand to top edge of element, cleaned again with alcohol, and trimmed wire to length. Cleaned inside of panel top carefully and then installed. Placed connecting wires into position and soldered with care. Before "closing", attached output to meter, applied light, and verfied repair---output now fine and solid during "tapping test" !

Had to carefully trim the bead of melted plastic along outside of opening edge with utility knife. Took a bit more thought on how to support element and seal the opening... Decided to use some high-quality, thin black foam-core seal material. Made a pattern by laying a small piece of paper over opening and running fingernail along edge to mark, then cut. Held pattern against seal material and cut it to size. Placed this into opening and very carefully worked edges under cover. Then used pattern to cut piece of clear, thin, hi-temp insulating plastic sheet to go on top---placed this into position and ran a bead of Loctite Go-2 glue around edge to seal repair. Now waiting for glue to cure overnight and hope to try with radio tomorrow...

Project pics below---any questions welcomed as I hope this will motivate others with a bad panel to attempt repair...

John


Attachments:
1ARF SOLAR REPAIR SILICN ELEMNT NEW WIRE.jpg
1ARF SOLAR REPAIR SILICN ELEMNT NEW WIRE.jpg [ 215.13 KiB | Viewed 89 times ]
2ARF SOLAR REPAIR PAPER PATTERN-FOAM SEAL PIECE.jpg
2ARF SOLAR REPAIR PAPER PATTERN-FOAM SEAL PIECE.jpg [ 181.88 KiB | Viewed 89 times ]
3ARF SOLAR REPAIR HI-Q SEAL FOAM PIECE INSTLLD.jpg
3ARF SOLAR REPAIR HI-Q SEAL FOAM PIECE INSTLLD.jpg [ 178.24 KiB | Viewed 89 times ]
4ARF SOLAR REPAIR HI-TMP PLSTC CVR INSTLLD.jpg
4ARF SOLAR REPAIR HI-TMP PLSTC CVR INSTLLD.jpg [ 229.12 KiB | Viewed 89 times ]
5ARF SOLAR REPAIR GLUED & CMPLT.jpg
5ARF SOLAR REPAIR GLUED & CMPLT.jpg [ 250.15 KiB | Viewed 89 times ]
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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Mon 18, 2019 5:37 am 
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Well done John! Perseverance pays off.


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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Mon 18, 2019 5:51 am 
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If I ever run into a similar problem, I'm going to send it to you. No way I'm going ever be able to do what you just did. :lol:

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 Post subject: Re: 1959 Hoffman Trans-Solar RP-706 project...
PostPosted: Feb Mon 18, 2019 6:09 am 
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Thanks much, Guys !

Ed---after what I've seen you do, know you can !

John


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