Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Hello, I recently recieved an old sears 125-xl slid state amp from my uncle. I've already replaced 4 transistors(no IC's in this old beast), and it sounds awesome. I've been trying to find out all I can about this old half-stack, but I always run into a dead end. The model number is 1423. it has tremolo and a very weak reverb. All I know is they were made from 1970-1972. Can anyone out there tellme anything about this great old amp?,or at least how to install a three prong plug on it?

Quote from: LJN on April 16, 2011, 12:12:51 AM
Hello, I recently recieved an old sears 125-xl slid state amp from my uncle. I've already replaced 4 transistors(no IC's in this old beast), and it sounds awesome. I've been trying to find out all I can about this old half-stack, but I always run into a dead end. The model number is 1423. it has tremolo and a very weak reverb. All I know is they were made from 1970-1972. Can anyone out there tellme anything about this great old amp?,or at least how to install a three prong plug on it?

3 prong plug is easy, don't know about the rest.  You will need a new power cord, then run the white and black wires to where they go now and bolt the green wire to the metal chassis.  That's it.

**edit**
Pictures would help, I'd love to see this beast.

Thanks for the advice. I'm sorry to tell you I cant post any pics, I wish I could. I'd love to show this old thing off. Unfortunately, I dont have a web cam or a clue as to how to use one. I can describe it to you, though. it has a slanted control panel that has sort of off white squares where the knobs are, the bare aluminum has some pits in it, I got rid of most of the oxidation with turtle wax rubbing compound(could be a useful thing to remember), the knobs are grey with aluminum center pieces, the casing was built by me(the original was destroyed about ten years ago), and the shaft on channel one's vol. is broken(but I have the knob). the amp is not much to look at but it's a tone monster! the speakers have also been changed. one is a celestion g-12 30, and the other is a jenson loudspeaker with 6969 printed on the edge. I use this amp almost every day, unless a thunderstorm is approaching(haha)  the original cord is intact all except for a spot where it was nicked, I taped that though. If I ever find a way to do it, I will try to post some good pics of it. thanks alot :)

Well, maybe somebody you know has a digital camera.
They are getting real popular these days. ;)

I'm not sure.The people I know usually dont use digital cameras that I'm aware of, I live in one of those types of places, in the mountains.

I imagined something like that.
Oh well. :lmao:
I hope at least you have access to plenty of good moonshine. ;)

no, not really. But I have 2 other amps(A 1976 peavey 260 H PA head, and a starcaster 15 G),And I can play as loud as I want. :tu:

If you all still want to see a picture of the old sears 125 xl, there's one like it on google images. It's the one with 10 knobs on it. If you get the chance, check it out. It was for sale on proxybid.com, and it sold for $100. Sure wish I could've bought it.  the reverb isn't too great, but these amps,In my opinion, get great tones for blues, hard rock, psychadelia, and with mine, I can get very close to an early led zeppilin tone. Of course if you're into a mellow sound, or a heavy metal sound, this is not the amp for you. they are very sensitive to feedback, and they get a ton of mid range. the picture should be in the top left corner, or somewhere thereabout. that's the closest thing to a picture of my amp I can possibly give you. these things are rare and unique. so check it out. If you can find one, and you're into vintage tone, get it! They're really great. 8)

There was also a Silvertone 125-XL which had the same chassis but nine sliders instead of ten rotary potentiometers.
Sears:
(http://www.proxibid.com/AuctionImages/2779/24683/Detail/002.jpg)
Silvertone:
(http://img518.imageshack.us/img518/2914/pict0115ix9.jpg)

It looks now you have to be registered at imageshack too to see the images.
Oh well.

Quote from: J M Fahey on April 18, 2011, 11:10:06 AM
It looks now you have to be registered at imageshack too to see the images.
Oh well.

They load fine for me and I don't have an imageshack account.

Yeah, That's the amp. I finally put the three prong plug on mine today. Seems like it changed the tone a little, could just be me, though. Anyway, Mine's not quite as nice as the one in the picture, I repainted the control panel by hand, and right next to the reverb and tremolo knobs, I painted my initials and a peace symbol. The covering on mine was brown, but it's still the same amp. that was the closest thing to a picture of mine I could give you guys. So now you have an idea of what we've been talking about. It's odd looking, but it sure does sound good. It responds quite well to effects too. I like this one a whole lot more than my first silvertone(an early '60's 1481). That thing gave me some shocking expieriences(hehe). Anyway, like I said, if you can find a 125 xl, get it. they really are great.

I'd like to add that my uncle told me that he thought the output on the anp was 50 watts. I just remembered that. I'd say that sounds about right. It seems louder now that I've put the three prong cord on it. It's not a small amp. It's heavy and about 3 feet tall, give or take 4 or 5 inches. I sure wish I could find out more about this old beast though. Any one out there know a way I could makr the reverb stronger?

I'd like to add that the reverb is supposedly some kind of wierd piezo type unit. it works, but it's very weak. Is there any way to modify the old beast to accept a more convetional(better) reverb tank? If so, how difficult might that be?

Without seeing a schematic I have no idea how to make the reverb stronger.  Even if you gave us some "guts shots" that could help.

Quotethe reverb is supposedly some kind of wierd piezo type unit. it works, but it's very weak.

Short answer: not, not really.
A slightly longer one:
*everything* can be repaired. even a burnt match, but in this case it would involve building a whole new amp, or thereabouts. Not worth the effort.

I figured as much. Maybe I'll just get a reverb pedal and put in front of it. Thank you for the advice.

I would like to add that a schematic for this amp is pretty much impossible to find. I'm not real good at reading them either.

There are a couple SS Silvertone amps floating around, a couple of them in the GT Tube amplifiers, no less.
They can't be *that* different.
The basic variations were whether they used an obsolete driver transformer for the power transistors or a more modern, conventional one with driver transistors.
The "technology upgrade" happened around the early 70's so you might have gotten either of them, depending on manufacturing date.

Wow, I didn't know that. I'm not sure, but I've been thinking it's a '71, could be a '72.never the less, This is the amp I've been searching for my whole life, I just didn't know it until I got the thing working. It's the first amp I've repaired, and it won't be the last. Although the next one will hopefully be a tube amp. I use this old amp every day. I wouldn't trade it for any fender, marshall, or peavey on the market. Now, if I could just get a gibson firebirdV to use with it, that would sound awesome. Thank you all for the advice. How can I tell what year this old beast was made in? also, where can I find some amp covering material? I'd like to dress it up a little. :)

Knowing the exact manufacturing year is not that important, since it's not a collector's item, so you won't get detailed obsessive serial number lists as you will on other luckier ones, but most parts have a date code, I'm certain for insurance or warranty purposes.
Once you find a couple matching ones, you know the amp was made sometime after that.
The typical format is a 4 digit number: the first two show the year and the others the working week, (01 to 52), easy to translate to month.
Read http://www.triodeel.com/eiacode.htm and http://home.provide.net/~cfh/pots.html

A potentiometer labelled A1M 137 7006 should be read as:
"A(udio taper/Logarithmic) Resistance 1M(egohm) made in (19)70, work week 06 (mid February) .
It would probably be found in a 1970 or 1971 made amplifier.
Since electronics parts have looooong shelf life, they may be found in *much* later amps, never in an earlier one (of course), unless installed later in a repair job (which also tells you a story about that "mint ... *never* opened collector's item).
As an example, yesterday I repaired an old 200W Fahey PA amplifier (my brand) , made in 1989 (many parts had 1987/1988 codes) with ST brand 2N3055 transistors code dated 931 (week 31 of 2009), made in Malaysia,  and TWT brand ceramic .33 ohm resistors labelled 902 (week 2 of 2009) , made either in Taiwan or China.
And we are talking a 2011 job, which is reasonable: 2 years from manufacturing to actual use, quite normal for parts which sit some time in a dealer shelf.

As a curiosity, post what you find on yours.

Tank you very much. I'll see what I can find out when I get the chance. From what I remember, I think the part numbers are of an odd sort, But at the time, I wasn't really looking for that. I'll be looking for them next time,though. There's a volume pot that needs to be replaced. I will write every number down that I see and post them.

Juan, I just took another look inside the amp. According to what you say about the date codes on potentiometers, these date to 1968. I found two different part numbers on the pots; 1-505-305 6845; and B-302-304 6847.Would that mean this amp was built in 1970? The transistors have 2 different part numbers as well; 2N5133, and 2N4250. I can remember the numbers on the transistors, because I had so much trouble finding replacements. I'll probably have even more trouble finding a replacement volume pot for the old beast. It's the channel 1 volume, I use channel 2.

Yes, 6845 and 6847 mean late 1968, compatible with a 1970 amp.
Your volume pot should match value and taper, nothing else.
Well, size too and probably the shaft to use the same knob, but nothing difficult.
Since they were non-switching but two very similar channels, only adding "evffects" to one of them, my guess is they are otherwise exactly alike, so volume pots should be the same.
Check it.
Those other numbers must be internal "house numbers" , but measure the pots with your multimeter and you're done.

Than you very much, Juan. I finally feel like I've found out some very valuable information on this old beast. I'm very greatful for your advice. I'm going to see if I can find a replacement for channel 1's volume, and hopefully I can order one and fix that. Hopefully, MCM has one. If they do, I can order it and have it in about 3 days. I'd still like to find out what the output is on this amp. I guess it's about 50 watts or somewhere thereabouts. I'm a guy who likes to know as much as possible about his instruments and amps. Thank you all for the replies. If any of you know anything else that migt help, please let me know.

I just found out that the celestion speaker in my sears amp's cabinet was made on may 13, 1980. It's date code reads EN13. The jensen speaker that accompanies it is most likley a 1961, The date code on it reads; 220144. But it makes no sense, because this is a ceramic magnet speaker. Could they have been making those as early as 1961? :-\ I understand that when the '70's came along, the codes were changed from having 6 digits, to having 7 digits. the later codes apparently show the last 2 digits of the year, insted of just 1. I guess that got rid of some confusion for the '70's and later models. :loco

Quote from: J M Fahey on April 26, 2011, 12:07:23 PM
Yes, 6845 and 6847 mean late 1968, compatible with a 1970 amp.
Your volume pot should match value and taper, nothing else.
Well, size too and probably the shaft to use the same knob, but nothing difficult.
Since they were non-switching but two very similar channels, only adding "evffects" to one of them, my guess is they are otherwise exactly alike, so volume pots should be the same.
Check it.
Those other numbers must be internal "house numbers" , but measure the pots with your multimeter and you're done.

I forgot to mention that I dont have a multimeter, but I'm gonna get one as soon as I can. Getting tired of the guesswork. I understand about the pots, and you are right, Juan. the volume pots have the same numbers, but theirs are different then the rest. I'll have to get a multimeter if I'm going to start working on amps and effects, just to be on the safe side. The transistors were easy bacause the amp had been lying opren for so long that each one had a lead that was rusted off. I was still very nervous about plugging it in because it had been rained in, wires were broken(I fixed those first), and it was just in awful shape. The volume on channel 1 broke when I tried to free it up. Channel 1 does work, but it's LOUD. :)

I found the original enclosure for the amp head yesterday( well, what's left of it). All I have to do is go back and get it. It sort of fell apart when I picked it up. I also found out where the celestion in the cab came from. My uncle put it there because one of the jensens went bad. He said he had bought the speaker at a flea market about a year before he bought the amp. In his words, something told him He'd need it. He said if he finds the other jensen he'll bring it to me. I sure hope it turns up.

I went and got the original enclosure to the amp the other day, there's not much left of it, But now I know more about how the control panel was originally mounted. I also found a digital multimeter for $12, and I bought it. I'll be measuring the pots in the amp next time I take it apart.

I have one more question about this amp. I'm pretty sure it needs a cap job because the bass control doesn't work like it should. I've been playing through it since december, and it still sounds great. My question is; Will it hurt the amp if I keep playing through it? Please get back to me on it.


                                                                                           Thanks, LJN

Quote from: LJN on June 13, 2011, 12:49:07 AM
I have one more question about this amp. I'm pretty sure it needs a cap job because the bass control doesn't work like it should. I've been playing through it since december, and it still sounds great. My question is; Will it hurt the amp if I keep playing through it? Please get back to me on it.


                                                                                           Thanks, LJN

No harm in playing it the way it is, it just won't work properly till you replace those caps.  Electrolytic capacitors are only good for 10 to 30 years depending on the quality, so it's probably time.

Thanks, Joe. You're right these capacitors are 41 tears old, plus they've been exposed to the weather for about 10 years. It's a wonder that this amp is working at all. It still sonds good, though. I still need to finish the new casing for the head, cover it, and replace the channel 1 volume pot. If playing it without doing a cap job won't do any harm, then I'll leave that part alone. I like the way it sounds as-is. At the moment, the case is just plywood with screws holding it together. It's not much to look at, but it serves it's purpose. I'm gonna fix it as soon as possible. I'm afraid to take it anywhere at present, It may fall apart. I've moved it, but the case felt pretty sturdy, though. But you know how these things go, It never happens in a place where you can just go ahead and fix it.

I take back what I said abot not being able to get modern heavy metal tones from this amp. I was playing around one night, and I got some of the most muffled, heavy sounding tones I'd ever heard. This amp WILL handle most any type of music you'd want to play through it.

In 1972 I purchased a shiny new Silvertone 125XL piggy-back amp right out of the Sears Catalog,  GOD AM I OLD!!!   

Based on my reading of the original owners manual, and looking at the schematic, I disagree about the power.  I believe that the RMS wattage was 125 watts.  The speakers were 12" Jensens, each capable of handling at least 50 watts RMS.  That sucker was LOUD.  Mine was the model with the 9 sliders, rather than the older, (but very similar) model with the 10 knobs.  My brother bought the older model used, and we used to jam with a young drummer, at Mike's Drum Shop in Santa Barbara.

The reverb, as I recall, was good and strong.  I don't think it was the same unit, as in the older knob model.  It sounded better, and there was plenty for me.  The Tremolo worked to absolute perfection.  I really liked the amp, but in later years, after getting married, and the kids coming along, I sold it and bought a Silverface Fender Princeton Reverb amp, which I loved for a number of years.

The piezo-type reverb was used by Danelectro, in their notorious "Reverb Box", of the mid 1960's.  They were horrid units.  I'm pretty sure the one on my amp was an improved design, as I remember the reverb on my brother's knob model sounded like crap.