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December 04, 2021, 08:25:35 PM

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1
Amplifier Discussion / Re: Hum increases with 3-prong cord
« Last post by Enzo on Today at 02:28:00 AM »
The nature of the power amp output stages is not likely the issue.  When you added the third wire ground, exactly WHERE did you attach it to chassis?

And for that matter, is the hum 60Hz or 120Hz?  (Assuming you are in the USA or Canada.  50Hz or 100Hz in 240v land)
2
Amplifier Discussion / Re: Sears Transistor Part Numbers equivalents
« Last post by Enzo on Today at 02:24:34 AM »
SIlvertone was simply Sears brand name for audio gear.  Sears and Silvertone are the same thing.  It doesn't matter who MADE the amps for Sears, likely DanElectro.  In any case, you apparently have the part numbers for them, so whoever owned that part number, look it up in NTE or similar to see what they would use.  It is a valuable clue.

Earlier amps may have used the driver transformer, but certainly the later ones did not.

DO you know the chassis number of that model?  Or post the schematic.
3
Amplifier Discussion / Hum increases with 3-prong cord
« Last post by Saransk on December 03, 2021, 11:24:59 PM »
It may be coincidental but a couple of the restored guitar amps I've done seemed to have an issue with running a 3-wire AC cord with ground and removing the polarity switch circuit.
The latest is a Gibson GSS100 head that has a more pronounced hum after a cord and capacitor replacement.
I've had the same issue with a Vox Berkeley 3 head and a Fender 1st generation solid state Deluxe Reverb
The amps have the same type of transformer driven "totem pole" output circuit. Could it be that this type has an issue with the hard chassis ground with the 3-wire AC cord?

A very frustrating issue as I haven't added/removed any of the circuit grounds, the inter-board wiring was the same.
Thanks
Michael
4
Amplifier Discussion / Re: Sears Transistor Part Numbers equivalents
« Last post by Saransk on December 03, 2021, 11:10:38 PM »
Not sure what the Silvertone part number would be as I don't think this version was a Silvertone design.
The last Silvertone designs all had driver transformers and  "totem pole" output stages like those of the Thomas Vox and Standel guitar amps.
I wasn't going to change any as it works, but the driver transistors appear to be replacements TIP 32A/31A.  The biasing diode is thermally connected to one but with the change I'd like to make sure the diode is connected correctly.
And to just add to it - the thermal bias diode is a STB567 -Stabistor diode.

The output circuit is very similar to the original RCA 70 watt amp "Quasi-Complementary" design, and the Kustom amps of the "tuck & roll" era.
Michael
5
Schematics and Layouts / Re: Randall RG100 G3 Plus
« Last post by mikebarg on December 03, 2021, 09:42:53 PM »
Thanks for the help. I've downloaded a pdf and am reviewing it.
6
Amplifier Discussion / Re: Sears Transistor Part Numbers equivalents
« Last post by joecool85 on December 03, 2021, 07:05:29 PM »
Probably something common like 2N3055.

Use the Silvertone part number and go to the NTE web site and look up their cross.  It may not be exact, but it will tell you what NTE thinks the part needs to be.

If the amp is working, I'd leave them alone.  Transistors don't wear out like tubes do.

I second this.  Also, if you provide us with pictures it may help.
7
Amplifier Discussion / Re: Sears Transistor Part Numbers equivalents
« Last post by Enzo on December 03, 2021, 05:22:11 PM »
Probably something common like 2N3055.

Use the Silvertone part number and go to the NTE web site and look up their cross.  It may not be exact, but it will tell you what NTE thinks the part needs to be.

If the amp is working, I'd leave them alone.  Transistors don't wear out like tubes do.
8
Amplifier Discussion / Sears Transistor Part Numbers equivalents
« Last post by Saransk on December 03, 2021, 05:12:46 PM »
I have a really nice, working, 2nd version Sears/Silvertone 200BLX head.
It has been upgraded once (caps) and sounds great
This is the later version with a more modern power amp - no driver transformer - looks like a Hafler or Kustom amp

The service manual lists all the parts with a Sears part number, no a problem with the passive parts, but no idea what the original devices were.  The driver transistors appear to be TIP devices (220 case) and not original.

Any place to find a cross reference for Sears transistor part numbers?
Thanks
Michae
9
Honey Amp / Re: Got my kit!
« Last post by smadin on December 02, 2021, 12:33:46 PM »
thanks! they are soldered, but could use a little touch-up.
10
Honey Amp / Re: Got my kit!
« Last post by joecool85 on December 02, 2021, 11:54:19 AM »
Photos of the build—I have a couple of these Trader Joe's tins, which I kept because I like the shape and size, a little more room to maneuver inside than an Altoids tin. I used some nylon standoffs and screws to hold it off the metal, which works well enough.

Looks like the input jack and power jack aren't soldered yet, or just not enough solder?  Neat build though, I like the enclosure a lot!
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