Opinions on my Guild Thunder 1 Twin

Hi again Adam.

I gotta agree with everyone about the power cord. Unless you play in a wet basement with one bare foot resting on a grounded water pipe, the chance of a fatal shock is unlikely, but the chance does exist. I wouldn't encourage anyone who has no experience in electronics to open up a tube amp and start melting solder joints, but for the price of an hour of shop labor, you might consider buying a good "how-to" book, a soldering iron, and spend some time learning how to do it. Tino Zottola was written a good series of books for the non-amp tech, which cover tube amp theory, safety, repair, and building amps from scratch. The safety and testing sections are invaluable. Even if you end up paying a tech to replace the power cord, the Theory/Repair book will help you understand how the amp works, and help trouble shoot when it doesn't.

In my humble opinion, if you like the "dark, creepy" sound of your amp, if the speakers aren't buzzing and the amp isn't humming,I wouldn't change a thing except for the power cord. I've experimented with alot of different amps and speakers, and I think original, vintage speakers almost always sound better. Those CTS 10's play a big part in that "dark, creepy" sound. The only reason I used the Celestions is because my T-1 came with NO speakers, and I just happened to have a pair of Vintage 10's in the shop. If you just GOTTA replace the speakers, I agree with capnjuan regarding the Webers. Best sounding, new production speakers you can buy ( I think), and they're on sale this month, too.

Capnjuan, I've been playing the amp alot lately, but finally took the amp out of the cab this AM to measure the HV secondary. It came right up to 285 VAC WRTG on pins 1 and 7. I must have blown the cobwebs out, cause it's
working fine now. I'll keep you up-to date with my Tremolo fix.

In regards to the 4 x 40 uF cap can, in practice I never use filter caps rated less than 450 volts when I build new amps or recap an older amp. However, the original Cornell-Dublier 4 x 40 uF cap I removed from my T-1 was rated at 350/300/300/300 volts. This make sense, since the SCHEMATIC calls for four 40uF caps rated AT 350/300/300/300 volts. Since the schematic also shows a primary voltage up to 125 AC, I think it's safe to say that a new replacement cap rated at 350/350/350/350 would be at least as good and as safe as the original.

Enjoy the amp, Adam. And thanks to everyone for the chit-chat. I really enjoy this forum. -Powdog

"Your cool if you don't know it, and if you know it then you ain't" -E.W.

adam79 said:

yep, i got one. when you connect the chord to the amp does the 3 prong cable connect the same way as the two prong one

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Except for the ground wire, yes but we'll worry our way through that when you have a cord (note spelling; guitars and trigonometry have chords, electric stuff has cords); 3 conductor, #18awg, type SO insulation, no longer than 6'. If you have to have longer than 6', then it needs to be #16awg, type SO insulation and, because it's thicker, you may need to ream out the hole in the chassis. Get the cord, we'll deal with the other stuff later.

adam79 said:

I'l gonna hold my breath and play the amp with the original chord, connected to a surge protector instead of straight into the wall jack, if that even makes a difference..?

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Okay ... but remember to breathe some ... no, the surge protector won't make a difference and don't play with your bare feet in a bucket of warm salt water ... get a cord. If we're going to walk you through this by post and reply, you'll need to post pics of the component side of the chassis so we can see what you see. If you don't know how to post pics here on the BB, say so; it'll help everyone be more effective helping you. CJ

powdog said:

... but finally took the amp out of the cab this AM to measure the HV secondary. It came right up to 285 VAC WRTG on pins 1 and 7. I must have blown the cobwebs out, cause it's working fine now.

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Hi PD; ... who knows ... good luck is where you find it.

powdog said:

In regards to the 4 x 40 uF cap can, in practice I never use filter caps rated less than 450 volts when I build new amps or recap an older amp. However, the original Cornell-Dublier 4 x 40 uF cap I removed from my T-1 was rated at 350/300/300/300 volts. This make sense, since the SCHEMATIC calls for four 40uF caps rated AT 350/300/300/300 volts. Since the schematic also shows a primary voltage up to 125 AC, I think it's safe to say that a new replacement cap rated at 350/350/350/350 would be at least as good and as safe as the original.

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You're probably right about 350V being adequate power handling and I thank you for making the point (I'm gonna go look at them) ... it's just that in this environment, Steve and I are inclined to preach safe amp sex ... which includes the widest available safety margins even if it means two overcoats instead of one. Thank you for your comments and contributions; I hope you'll stick around for a while ... pull up a chair. CJ

capnjuan said:

powdog said:

... but finally took the amp out of the cab this AM to measure the HV secondary. It came right up to 285 VAC WRTG on pins 1 and 7. I must have blown the cobwebs out, cause it's working fine now.

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Hi PD; ... who knows ... good luck is where you find it.

powdog said:

In regards to the 4 x 40 uF cap can, in practice I never use filter caps rated less than 450 volts when I build new amps or recap an older amp. However, the original Cornell-Dublier 4 x 40 uF cap I removed from my T-1 was rated at 350/300/300/300 volts. This make sense, since the SCHEMATIC calls for four 40uF caps rated AT 350/300/300/300 volts. Since the schematic also shows a primary voltage up to 125 AC, I think it's safe to say that a new replacement cap rated at 350/350/350/350 would be at least as good and as safe as the original.

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You're probably right about 350V being adequate power handling and I thank you for making the point (I'm gonna go look at them) ... it's just that in this environment, Steve and I are inclined to preach safe amp sex ... which includes the widest available safety margins even if it means two overcoats instead of one. Thank you for your comments and contributions; I hope you'll stick around for a while ... pull up a chair. CJ

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You guys are just too good - the level of expertise available here is beyond price.

Thanks all.

AND CHANGE OUT THAT CORD, ADAM79 - we'd hate to lose you, expecially since we just got you!

Hey all.

I've been thinking about your situation Adam. You know, until you have the funds or know how to change out the power cord, you could always use an isolation transformer. I picked up three really nice Stancor units on eBay about a year ago for $25 bucks. This way you will be isolated from the house current.

About 5 years ago when the price of little tube amps started climbing, I bought half a dozen little 35Z5/50L6 based amps for bedroom jamming and recording. The little Magnatones, Oahus, Nationals and Kays sound really cool, but the two wire power cord and grounding schemes leave the chassis hot. I kindly refer to these as my "Death Amps".

In an attempt to make them safer, I tried installing isolation transformers inside the cabinets. Unfortunately, this caused alot of "hum", and also killed the tone a little. After returning the amps to stock, I picked up the eBay isolation transformers and this really worked out nice. The transformers are a stand alone unit, with about a foot long cord going in and comming out. So just plug the isolation tranny into the wall, the amp into the isolation tranny, and you're now isolated from the wall current.

I would still swap out the power cord. And while you in there, if the amp is humming when you crank up the volume, you might as well change out the filter caps and add a bleeder resistor. With the chassis grounded thru the three wire power cord, the 330 ohm/pilot light array on the HV side will bleed the caps down to about 60 volts. A 220 ohm resistor added at the first filter cap node will bleed off all filter capacitor voltage whenever you turn off the amp. Much safer for future tech work.

Good luck.

This weekend I came to the conclusion that I disliked the amp and was gonna sell it.. When I unscrewed the back panel to take a picture of the tubes and speakers, I noticed that the two power tubes and rectifier tube were half plugged in (the shipper didn't take the tubes out before packaging the amp). I plugged the tubes back into their sockets and now the amp has grown a pair of balls; when I crank the volume to 10, the tubes break up well and I get a nice distortion sound. All the tubes say "Guild" on them, so I assume that they are the original ones that came with the amp. I'm now 100% satisfied.

There is nothing, nothing, more satisfying than a simple self-found fix to an aggravating problem. Nicely done.

Now fix that cord, OK?

adam79 said:

... when you connect the chord to the amp does the 3 prong cable connect the same way as the two prong one, or do you need to install more parts to make the connection capable of powering the 3 prong?

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Hi Adam; glad you got it running better ... yes, they work better when the tubes are seated correctly. About the power cord ... This is a shot of a Silvertone 1471 that belongs to a member here ... his isn't colored coded ...



This power cord has three wires: brown, blue, and green. The red circle is a strain relief bushing that is held in place by the lip of the chassis hole, pinches the cord, and prevents it from pulling the solder connections apart in case someone stumbles over it. 3-wire cords are thicker than what you have; the hole either has to be enlarged by reaming or drilling or ... you go to Plan B discussed below.

The easy part of this is what's going on in the magenta and green circles; one leg of the new cord (brown wire above) goes where the old one did on the switch and the other (the blue wire) goes to one side of fuse ... where the old one went. The switch is the pic and all the amps I work on is new which means the supply wires to the power transformer have to be de-soldered and re-soldered to the load side of the switch and fuse post.

The blue circle is the ground wire secured under one of the power transformer bolts. You need some kind of crimp-on or solder-on terminal; spade or loop, to put on the end of the ground wire, back the bolt out, trap the terminal under the nut and do the Tighten Up.

Plan B: tie a knot in the power cord on the inside side of the chassis to keep it from being pulled back through the hole and thicken the cord with black electrical tape to protect the cord from being chafed at the lip of the chassis. If your friends see this work though, you can expect excess dandruff and BO.

In a week or two, I'll be changing a cord on another amp; will do the pics but get a cord and take and post some pics of your amp. CJ

Hey Guys.

I don't want to steal anyone's thunder, and I kinda feel like I'm beating this subject to death. That being said, when I swapped power cords on my T-1 Twin last week, I took alot of photos. Included are shots of the power switch, cord, polarity switch, and filter caps before and after the upgrade. If anyone is interested, let me know and I'll send them.

Cheers! -PD

Hi PD: if you have a web-based photo account, consider dropping a pic or two here in the thread, especially the fuse post and switch, dump the others in your photo account, and leave us a link here. That way, there will be a reference source for some helpful T1 pics. I started to dump some more pics here but realized that the amps were early version T1 RVTs with the fuse in a clip and not the later models with the fuse in a post; that is, yet another amp that didn't apply. Anyway; your choice - here or there but the pics will be helpful either way. CJ

Hey Guys.

Here are the pics of the switch and fuse before and after the upgrade. I'm new to Photobucket, so I hope these work.

http://i452.photobucket.com/albums/qq24 ... ics381.jpg
http://i452.photobucket.com/albums/qq24 ... ics411.jpg
http://i452.photobucket.com/albums/qq24 ... ics391.jpg
http://i452.photobucket.com/albums/qq24 ... ics413.jpg

Cheers. -PD

Hi PD; they worked fine, thank you. If you decide to do something with your can cap, this is one solution: Weber 3X40ufX450v can caps - and ... they come in colors. For lack of space for two loose caps, the chassis was punched for the second one near the power supply and the fuse was moved from a clip to a post accessible without taking the chassis out. (photo courtesy of the President of the New Zealand chapter of LTG :wink: ) Thanks again. CJ

Hey CJ.

I have the highest regard for Ted Weber and his speakers. Using the colored Cap Cans in an application like the T-1 reverb pictured is fine. Unfortunately, the last time I used one was in a 18 watt design that placed the Cap Can next to a 5U4 rectifier. Since the metalic shell of the Weber Cap Cans are attached to the plastic base using hot glue, it only took about 30 minutes before the glue melted, the shell fell off, and hot glue dripped down onto the speaker cone.

I am unaware if Weber has changed their manufacturing methods. I am sure most applications are fine, but in those where the cap can is placed close to rectifier or power tubes, beware. I ended up using a heat gun to melt off the rest of the glue, scraped both surfaces clean and reglued the shell with epoxy.

I have three files with Photobucket regarding this amp. The four pictures above, one containing gutshots of the amp, and a third containing pics of the cabinet refurb.

Cheers. -PD

Hi PD: hmmm ...discouraging remarks about the Weber can caps ... considering the application, hard to believe all of them are that vulnerable to heat ... I mean it isn't like they're built to go in refrigerators ... If you don't mind, I copied down the link to your two Guild T1 Twin PB albums. Mighty spiffy work on the cabinet; is that new tolex? Came out great!

http://s452.photobucket.com/albums/qq247/Powdog562/

Hey CJ.

The Weber Cap Can thing is a bummer. I've meant to get in touch with Ted and ask him if this a common problem, and if the construction methods had changed. I due respect, he should probably get this kind of feedback to properly address any problems. I think I'll email him tomorrow. Since the meltdown incident, I've been using JJ's, which come in Marshall and Fender values and cost between 10 and 15 bucks.

Ahhh, the cabinet. This was actually a nice suprise. When I bought this amp off eBay for $77.50 (item # 180296717837) "AS-IS", not working, broken switch, no speakers or knobs, I expected the worst. The amp chassis looked pretty clean in the few pics, but the cabinet looked as if it had been in a moldy basement for 20 years. I figured worst case scenario, new cabinet; best case, new tolex. As it turned out, the cabinet, which is 3/4" pine, is tight, odor free and has solid joints. The filth came right off with Simple Green and a brush, which I followed with some Armour-All type stuff. I don't imagine I will get the grill cloth any cleaner, but I really don't want it to look new anyway. It looks it's age, and that's pretty cool. I wish I looked as good!

On the tremolo front, there are two capacitors that follow the 390kohm resistor comming off the wiper of the tremolo pot. I changed the .01 uF cap to .02 uF and it slowed the trem speed down some. I think I will also swap out the .022 uF cap that goes to pin 1 of the 12AX7 to a .047 uF. This will bring the values of the two capacitors to the same level of similar amps. I like the depth level, but really like it when the tremolo has a slow, deep throb (amp sex?).

Help yourself to the pics at Photobucket. And Adam, we haven't forgotten you. If your interested, I would be glad to do any upgrades to your amp. I wouldn't think of charging you anything. If you live near the Sacramento, CA area, we could meet. Or, remove the amp chassis from the cabinet and send it to me. I would imagine that shipping is considerably less that shop time. Consider it.

Cheers. -PD

powdog said:

... I wish I looked as good! ...

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Hi PD: ... alot of that around here ....

powdog said:

On the tremolo front .. slowed the trem speed down some.

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Sounds like you have a good solution.

powdog said:

help yourself to the pics at Photobucket.

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I thought the pics might help some of the BB broz; ... for my part on 3-wire cords ... been there, done that, and have the tee-shirt. CJ