Rebuilding a Silvertone 1484

[cobalt]

Hello All,

I have most of the parts I need, maybe.... I have the caps to rebuild the doubler, wondering if I should replace diodes too. Will 1N4007s do the trick? Seems like a bit of overkill. Also looking for options for the can cap, I have three single caps that will work, but there isn't much room in there. Will have to replace some pots too, no biggy. I was given this as a basket case, it has no knobs and no cab to speak of.

Well thanks for any help you can give.

weirddave

[sluckey]

I would only replace the diodes if they were actually bad. 1N4007 would be a good choice.

[Platefire]

Have you performed any test to make sure the transformers is good? I rebuilt an old Gibson amp about a year ago that had been sitting in a storage shed for years and the rats had chewed the reverb and output transformer up. That would be good to know because they are some of your most expensive parts. Platefire

[SoundmasterG]

For the can cap, you used to be able to get an exact replacement that fit right in from Vibroworld, he custom made them, but he closed up shop years ago. I got the last one for my 1484. You can get a custom one from Ted Weber, but it won't fit exactly....you can even have them make them with separate grounds which is better than one common ground if you can control grounding. In the 1484 it doesn't really matter too much as even if you improved the grounding the amp still hums a lot stock and nothing you can do will change that. Aside from those options, you are left with using a 2xxx can cap that is larger and cutting the hole out and using a discrete cap inside the chassis, or just leave the can in place but disconnect it and use discreet caps inside the chassis.


When I rebuilt my 1484 and my brother's I replaced the diodes with 1N4007's....the old ones looked sketchy to me, but they are probably ok. Replace them if you want.


Somewhere on here about 4 years back I had a long thread on the 1484 and what I did to my brother's if you're looking for mods....you can make it sound cooler but it is a LOT of work.


Greg

[cobalt]

Thanks guys,

I hadn't thought about the "soundness" of the transformers..... I just checked and they are close to resistances on schematic.

I guess I'll have to drill out cancap, and do three separate caps through the chassis. Might have to nibble a bit for clearance. The resistors here have drifted badly, 68K reading 75K.

Replaced diodes, because they were in the way.

Will also add a proper speaker jack, IEC power input(more nibbling around convenience outlet), and maybe a bias pot.

This is a functional rebuild, not a restoration.

Thanks again! Any more ideas, bring 'em on!

weirddave

[SoundmasterG]

Thanks guys,

The resistors here have drifted badly, 68K reading 75K.

Not surprising...they were originally 20% tolerance parts.

Will also add a proper speaker jack, IEC power input(more nibbling around convenience outlet), and maybe a bias pot.

This is a functional rebuild, not a restoration.

Thanks again! Any more ideas, bring 'em on!

weirddave

I added an IEC, speaker jacks, and adjustable bias pot to my brother's.....the stock tap is a 4 ohm tap for the 1484...the other tap is a 2.6 ohm for the 1485. To add the bias pot you will have to add a voltage doubler circuit to the bias to be able to get useable voltage. For the IEC I just removed the convenience outlet and nibbled and it worked fine. The chassis is aluminum so its easy to work with.


I was looking for the thread of the mods to my brother's from over 5 years ago but couldn't find it. I did pretty much whatever you could imagine to a 1484 and documented the pros and cons pretty thoroughly, but I can't find that thread right now. You can boost the power of the amp a little by adding a filtering stage and connecting the screens to the stage in the doubler after the power tubes....so they would have three stages instead of the stock two. It will take the RMS power to 30 watts from the stock 25 watts. The OT is very small on these amps....if you go with something larger and bump the screens up you can likely get to 40 watts or so with much better overall frequency response, but the mid focus is part of the character of the 1484 too. On my brother's I added an EF86 to channel 1, added a Fender reverb circuit and tank, put verb and trem on both channels, bumped up channel 2 for more gain, and redid the whole preamp layout so the signal didn't cross back on itself. I also redid the grounding and isolated it from random chassis grounds. Due to the increase in gain, it hums more than stock and that can't be avoided due to the very poor PT location. The amp sounds good, with more power and better reverb, but still some Silvertone character since I stuck with the stock OT and stock phase inverter. I had to revoice the tone stack in channel 2 as when I increased gain the previous stock circuit was now affecting bass frequencies. I left it as the stock Baxandall tone stack but I shifted frequencies by changing parts values. I have pics but they are blurry....but I can share if you want. I can also get some new pics as my brother wants me to mod something on it again. The never ending project! :) YMMV.


Greg