Silly Silvertone 1482 Excursion :>)

[Platefire]

Yesterday I set off to play at a place with my 1482 because I though it would be perfect for the small room. Got there, set up and when I was doing my first song encountered terrible static in the signal through the instrument channel and ended up ending the first song short of completion because of the static. I was using a Boss RV3 for a little reverb/delay---so I switched channels and the static quit.

So I was thinking Ah Ha! something is amiss in the Instrument channel. When I got it home--yes it was still doing it--testing it with the same set up I used that day. Tried different tubes--still doing it, checked for faulty ground---no problem--so pulled the chassis and checked everything on that channel, cleaned sockets-cleaned jacks--couldn't find anything? Hooked it up with the chassis out and it worked perfect. So I put  it all back together and hooked it back up complete with reverb pedal and bang! it was doing it again!!! So I plugged up without the pedal and NO PROBLEM. Then I hooked the guitar back up with the pedal with a different path cord from the pedal to amp--and then the problem was gone. It was the patch Cord all the Time!!!

So what fooled me was when I was playing at the event and switched channels, then it quit, I automaticly assumed it was in the amp channel but apparently changing channels just put the patch cord in a different position where it wasn't shorting out and worked for the remainder of the event. Because of that initial assumption, I put myself through all the trouble shooting for a silly patch cord.

The moral of this story--that I should already know--is remove all extra stuff/pedals/cords prior to amp before testing an amp for a problem.    Platefire

[6G6]

I know it has been said many times before, but
don't overlook the simple stuff. 

[TubeGeek]

Funny how these things happen.  What usually gets me is I troubleshoot a problem thinking it's in the circuitry when all along it was simply a bad tube.  Of course it's the last thing I decide to replace.

[Platefire]

Yeah if you got knowledge and don't use it, the joke is on you!  


While we on the subject of my 1482----while I was working on it I noticed the mic channel is a lot livelier,  brighter and stronger than the instrument channel. The main difference in circuitry is on the mic channel I have a new metal 2 watt 2.2K cathode resistor and the instrument channel has the old original carbon comp 2.2K resistor. Also I should mention the mic channel doesn't have a 68K grid resistor like the instrument channel. I'm just wondering if it's the difference in type of cathode resistors that's making the difference. I checked both resistors and they both read close to 2.2K. I checked all the other things effecting both channels including voltages and coupling caps and everything seems the same. The cathode resistors is the only thing I can point to that could be making a significant difference? Any opinions? Platefire

[sluckey]

Change the tube.

[Platefire]

Yeah I've got an old vintage Heathkit/Mullard in there. If the instrument chan stage is kind of weak, it could be it. I'll try that and post the results. Got a new EH I can try in there. Platefire

[TubeGeek]

Change the tube.

 

[gldtp99]

Yes, the V1 tube may have triodes that aren't matched very well----- also check the 330k V1 plate resistors---- the cheap resistors that Danelectro used in these amps are prone to drifting.
I just had a 1482 on my bench and I replaced the badly drifted (high) 330k V1 plate resistors with 150k's (and added 4.7uF bypass caps across the 2.2k V1 cathode resistors).
The amp still has that cool early breakup but has more definition------ and no hiss. The orig drifted 330k's added hiss along with flubby, early breakup.
All orig tubes in this one---- V1 and V2 are Holland Amperex, labeled Silvertone like all the rest of the tubes.
The orig CTS alnico speaker compresses nicely when pushed and the amp is a huge amount of fun to play !!
One of my amp customers (1948 Knight PA head converted to Tweed Pro 5e5-ish circuit) was there to help test it out and it was loving it--- It was hard to get him to stop playing so I could test it out..................gldtp99

[Platefire]

Man! This thing is driving me nuts. I went back to test it with a new tube in V1 and the static showed up again. It wasn't the patch cord after all---I went back and pulled it out of the trash where I had chunked it.  

OK--I checked with two different guitars and two different cords. The static is in the instrument channel and is kind of intermidant. It don't show up so much a low volume and seem to increase as you turn the volume up and play. The static only occurs when your playing. It's not the tube because it did it with the new and old one. My experiance in the past with that kind of static has been a bad ground connection but when I do continuity checks all grounds check good. Isn't a whole lot there between the input and tube to go wrong.

Bare in mind I'm trying to keep this 1482 all original(in spite of original bad practice) and I have another 1482 that I do all the mod stuff to. This original has input jacks that uses the jack connection to chassis as ground. That's for the 1 megs and both preamp stage cathode resistors to ground. They all are connected to the input jack ground lug. There is no seperate ground wire from jack ground term to chassis. This input jack ground connection to chassis would be my first suspect. Any other ideas? Platefire

[John]

Sounds like lots of possibilities. Cracked solder joint, maybe a ground showing continuity but actually having resistance,  or maybe even a resistor where the lead is not firmly attached to the body... there's a break in the chain sommares!

[Platefire]

Well I'm not going to say for sure I've got it corrected but right now it's doing good.  

I tore it back down this evening and went first for the mic input jack that has both cathode resistors grounded on it. When I first put a socket on the input jack nut it turned without any effort. In other words it was borderline lose. Took it out of the chassis hole and burnished it up around the hole, put some contact cleaner on it, put it back into the hole and tightened it down good. It hasn't had static anymore so far. I hope that got it.

Now! Back to the original subject---testing another tube to see if that was the difference in the sound of the two channels. I tried a brand new EH 12AX7. Still though it may not be a mountain of difference, I still prefer the mic channel. It's just stronger and I prefer the tone better. It's got a cleaner tone than the inst channel. So if you was using a A/B/Y pedal for channel switching, you would want the mic channel for clean and inst channel for distortion. Platefire

gldtp99---I'm a 1482 nut because it was my first amp in the 60's. My first experiance with tube breakup--even though I didn't know what was going on then??    I think it's a cool old amp. I've got two. One stock and one I've done a lot of mods on. Even though I've done a lot of what I would think of improvements to the modded one, I think I still prefer the original. I tell you one part you don't want to mess with is that back-plate. Even though it's only semi closed, that backplate really gives it a lot of depth. My original one has a Fisher Speaker code 1056-516 dated 16th week of 1965. About the time I graduated from high school.      

[gldtp99]

I agree about the back plate----- mine came without the orig backplate and the seller included a cut-to-fit MDF panel with the amp----- when testing out the amp in the cab for the first time, with my friend playing it, I much preferred the amp with the back panel on.
The amp sounded pretty good through an 8 ohm Marshall 4x12 on the bench, too.
I tested all the orig Silvertone branded tubes (all RCA except for the Holland Phillips in V1 and V2) with my new Orange Valve Tester and all tubes are strong.
I put in a new grounded AC power cable, removed death cap, routed the Hi AC supply as fuse, switch, PT.
I put in a 330 ohm/25 watt cathode resistor and new 22uF/100V bypass cap on the output section----- cleaned jacks and pots.
I had people coming over tonight to demo this "little ugly amp", as they called it, tonight while I was working on my latest PA head conversion, a Stromberg-Carlson AU-58A.
They were blasting the 1482 straight in and with my TS9 and an Analog Delay---- got lots of positive comments and a promise to come back and buy it..............................we'll see if the one guy is really serious or not------ these are cool sounding small amps----- the breakup/compression sounds and feels just right--- and this one is almost dead silent when cranked (with guitar vol turned down)----- no hiss, no hum, no anything until the guitar is turned back up------I didn't think any old Silvertone amp was capable of this------ my current 1484 and my 1485 are good sounding and very cool amps but are not as noise free as this 1482------ this is the first 1482 I've owned but it might sell before long.................................gldtp99

[Platefire]

Well You shouldn't sell it---it's a keeper!

Well since we are talking about 1482's already, on my stock 1482 there isn't much to talk about or show because everyone is familiar with its setup. I'll talk a little about my modded one. On this one all circuit mods are switchable so that by turning the mods off you can get back to original 1482 configuration as follows:

1-Installed a 3/8" plywood speaker baffle and used the original 1482 grill cloth over it.

2-It's got a Weber Speaker that G Weber made especially for a 1482 for the Vintage Silvertone Forum about 10 years ago. The only problem was the speaker was a little too deep and the back plate wouldn't go on an be flush. I ended up making a special backplate to allow the magnet to stick through. I think I'm going to do a mod to the existing back plate as shown to cover the opening to make it more like the original back plate soundwise. I had to switch the OT tap to the 8 Ohm for the Weber.

3-Mic channel is a bright channel in that it has a Fender 5E3 tone stack. Also the 25uf/25 cathode bypass cap is switchable.

4-Inst channel has two switchable bypass caps 22uf and 47uf. It also has two switchable negative feedback loops. Tone stack is original. I did away with one of the inst channel input jacks to install a switch.

5-The input jacks were changed out to fender type set up with hot switchable to ground when unplugged and also have the jack wired to ground on a adjacent terminal strip. The cathode resistors are no longer wired to the input jack but to a terminal strip.

6-Added a standby switch.

7-Abandoned the old can filter caps in place and installed new filter caps and power rail resistors on terminal strips.

Attached is a schematic for 1482 #2.

Also here is a link to my original & Modded photos, if you want to look.
http://www.flickr.com/photos/12623503@N04/sets/72157601870694620/

[Platefire]

OK. I've done enough testing to say the static problem is now fixed. The problem was the mic input jack had a intermittent ground connection which is also was the ground for the cathode resistors + grid 1 meg to ground.

The Mic channel is a little brighter and with a little more punch that the Inst channel for what ever reason. Tried different V1 tubes and it didn't change. My personal opinion is it's the difference in the carbon and metal cathode resistors. The major circuit difference other than cathode resistors is Mic channel has only one input without any grid resistor and Instrument channel has two inputs with 68K grid stoppers. Plate voltages are the same and there is no cap leakage of DC into AC area.

On an added note on my modded 1482#2, I pulled the Weber Speaker and tried my recently acquired Emenance Patriot Cannabis Rex and it sounds much better, so I left it in there. The Weber is just to bright and clean and restricts the 1482's natural breakup. The Cannabis Rex allows the 1482 to do its thing. So I glad to have both 1482's up to speed. Platefire