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Author Topic: New amp day! Silvertone 1481  (Read 1393 times)

galaxiex

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Re: New amp day! Silvertone 1481
« Reply #15 on: June 18, 2017, 05:23:11 PM »

On to other things...

Need a new speaker baffle, so a short time in my shop with the table saw and jig saw and we have this...

First, the old baffle and careful removal of the grille cloth.

Transfer dimensions to a piece of 1/2 inch plywood.

Cut relief on the corners so the new baffle will slip into the cabinet.

Then drill some holes and paint flat black.
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galaxiex

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Re: New amp day! Silvertone 1481
« Reply #16 on: June 18, 2017, 05:26:59 PM »

Here's the old speaker (original?) and O/T.

Someone put some goo around the cone at the edge surround trying to "save" it.
It's done.
Cone has a small tear and makes crunchy/crackling noises when you touch it.
The paper is very dry and brittle.

For the record... this speaker did "work" when I got the amp, but it definitely needs a recone.

Meanwhile, I have a few 8" speakers I can try out once I get the baffle installed. (waiting for paint to dry)
« Last Edit: June 18, 2017, 05:34:33 PM by galaxiex »
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galaxiex

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Re: New amp day! Silvertone 1481
« Reply #17 on: June 18, 2017, 07:45:32 PM »

There!
Speaker baffle done!

I think I'll call this amp "Bruce"  ;)

Now the 2 week wait for the new O/T to get here...
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Enzo

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Re: New amp day! Silvertone 1481
« Reply #18 on: June 18, 2017, 09:21:56 PM »

How about a thorough inspection.  measure for primary resistance right at the transformer wires.  it may have opened, but there is nothing inherent in changing to a grounded power cord that would stress a transformer.
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galaxiex

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Re: New amp day! Silvertone 1481
« Reply #19 on: June 18, 2017, 10:36:41 PM »

Thanks Enzo,

Yes, I should do more checking.... however...

I'm embarrassed to admit.... "I" may be the cause of the failed transformer.

You see, I drilled a hole for the secondary wires to go inside the chassis so I could install the speaker jack.

Foolishly I did this with the transformer still bolted in place... do you see where this is going....

That's right, the tiny pilot drill I used, punched through the chassis and nicked the winding's.  :grr

I then of course, removed the Tx and made the hole big enough to install a grommet for the wires.

Then inspected the Tx carefully with a magnifying glass and did not see any real damage, but the drill bit did go a small ways into the winding.

Fairly sure I screwed it up.

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joecool85

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Re: New amp day! Silvertone 1481
« Reply #20 on: June 19, 2017, 06:05:50 AM »

Thanks Enzo,

Yes, I should do more checking.... however...

I'm embarrassed to admit.... "I" may be the cause of the failed transformer.

You see, I drilled a hole for the secondary wires to go inside the chassis so I could install the speaker jack.

Foolishly I did this with the transformer still bolted in place... do you see where this is going....

That's right, the tiny pilot drill I used, punched through the chassis and nicked the winding's.  :grr

I then of course, removed the Tx and made the hole big enough to install a grommet for the wires.

Then inspected the Tx carefully with a magnifying glass and did not see any real damage, but the drill bit did go a small ways into the winding.

Fairly sure I screwed it up.
Bummer. However I feel for you. I did a similar thing where I was putting a heat shield back onto my wife's car. I had to drill a hole for the rivet and it was to go into the spare tire housing...I didn't remove the tire first. Made for a funny moment at the tire shop when I told them I drilled the tire LOL.

Sent from my XT1055 using Tapatalk

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galaxiex

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Re: New amp day! Silvertone 1481
« Reply #21 on: June 19, 2017, 09:01:47 PM »


Bummer. However I feel for you. I did a similar thing where I was putting a heat shield back onto my wife's car. I had to drill a hole for the rivet and it was to go into the spare tire housing...I didn't remove the tire first. Made for a funny moment at the tire shop when I told them I drilled the tire LOL.

Sent from my XT1055 using Tapatalk

Thanks Joe, that's a funny story.   :)

Ya, I'm sure anyone that works with their hands has messed up somewhere, sometime, and done something boneheaded.
I know I have, and not just when working on music gear.

I've been in the transmission repair industry for nigh on 40 years now and have witnessed, and done, some really stupid things.

One doozy I'll never forget....

Taxi cab came in the shop cuz the tranny is not working... Ford Crown Vic rear wheel drive.
Ok, so pull the tranny out see whats broken...

The guy pulling the tranny removed every single bolt holding the tranny in the car and it refused to come out...???
Like it was "stuck" up in the car... WTH.

Turns out the driver had it at a place to install "Taxi cab gear" you know, the meter and radio and such...

Well they mounted it on the transmission hump and.... surely you can guess now...

Yup, they use reeeely long screws and drilled and screwed right down into the transmission to install the meter and radio. DOH!

Glad it wasn't me that did that!

(you didn't think I was gonna tell of any of my boneheaded screw ups, didja  ;)
this one with drilling the Tx was enough.
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galaxiex

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Re: New amp day! Silvertone 1481
« Reply #22 on: June 19, 2017, 11:12:41 PM »

Just thought I'd throw up a schematic for this...
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J M Fahey

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Re: New amp day! Silvertone 1481
« Reply #23 on: June 22, 2017, 08:47:20 PM »

Probably wire was quite corroded and barely held for the initial tests, then any knock might have finished it off.
Look closely , inder good light and with good glasses, you might have it split very near the terminal, simply because only the wire end gets scratched for soldering, the rest is still covered in protective enamel.

The point being that maybe 1/2" or less of fresh copper wire saves your transformer.

As of the enamelled wires directly being the external connections, itīs often done in low voltage transformers (think 6V or 12V) , it saves some assembly seconds and is relatively safe,since that wire is usually thick.

It woud be dangerous on primary fine wire, and VERY frustrating.
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galaxiex

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Re: New amp day! Silvertone 1481
« Reply #24 on: June 22, 2017, 09:52:50 PM »

Thanks JM,... but

Naaaah  the transformer is gakked!

I peeled back some of the lacquered paper and the drill bit went in right between the thick sec wind and the tiny primary.
With the paper peeled back I can see several broken primary winds right in the middle.

Only way to save this one would be a rewind. Probably not worth it.

I'll keep it with the amp for posterity.  :)
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galaxiex

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Re: New amp day! Silvertone 1481
« Reply #25 on: June 23, 2017, 10:29:42 PM »

Sooooo, as per the schematic attached above, the original O/T secondary went straight to the speaker.
No connection to the chassis.

Since I am installing a speaker jack,
I have the option of installing an insulated jack that obviously, would also not make any connection to the chassis.

If I were to install a non-insulated jack, would it then make some difference as to which side of the secondary should be connected to the ground side of the jack?
IOW, is there a phasing issue that I need to be concerned about?

TIA
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Enzo

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Re: New amp day! Silvertone 1481
« Reply #26 on: June 23, 2017, 11:13:46 PM »

Phasing really only matters when the same signal is fed to multiple amps.

There appears to be no negative feedback loop, so phasing doesn;t matter there either.

usually output transformers identify hot and cold lead by color.  SO good practice would be the cold side to chassis.
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galaxiex

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Re: New amp day! Silvertone 1481
« Reply #27 on: June 24, 2017, 02:09:02 AM »

Cool.  8)

Thanks Enzo.

Hopefully when the new O/T gets here, it will have something to ID the leads.

Edit; Oh... yes it does...  I ordered this one...

https://www.amplifiedparts.com/products/transformer-hammond-output-replacement-fender-5w-7k
« Last Edit: June 24, 2017, 02:11:07 AM by galaxiex »
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galaxiex

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Re: New amp day! Silvertone 1481
« Reply #28 on: June 29, 2017, 09:18:15 PM »

New output TX came in.

Amp is working again, Yay.  :)
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jfetter

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Re: NAD!
« Reply #29 on: June 30, 2017, 03:52:25 PM »

Thought I'd put this here since its a tube amp.  :)
What makes you think that?  :o
Last time I checked, site name said "SS"  :o

its kinda funny, i've put up a lot of diy data on hybrids on another site and it gets no love , even the students get upset. if i put test plots and schematics in SS they cry, then if i put in Tube section they cry. Its hybrid and homeless. Nice to see a hybrid section here.

congrats on your amp find.
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