New member with new toy ( Thunder 1)

Brendan

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Delta362 said:
Brendan,
I never would have thought the electrolytic cap was marked backwards. Your tech was a great help in finding that.

I finally got around to ordering my caps and resistors this week. I'm not expecting them until the weekend at the earliest. I'm hoping to tear into it shortly after I get them. I also ordered and received those same 3PDT switches, a rectifier tube and 4 of the 6GW8 tubes.

When installing the 3 prong cord, did you install a socket like a computer or just hard wire it? I've got an extra socket that I may install, but need to talk with the owner first.

It took him all of 5 seconds to see it. http://www.soursound.com Great guy.

I hard wired it. I thought about doing the socket, but just went with the cord available at Antique Radio Supply. Glad to hear parts are on the way. Look forward to seeing how it turns out. Good luck!
 

capnjuan

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Delta362 said:
I have relooked and re-confirmed that the tremolo on/off switch is drawn correctly with how my amp is currently wired. It also matches the grounded condition = on that is found in the RVT schematics.
Hi Mike; okay, you have the amp in front of you. Good luck! J
 

jp

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Brendan said:
It took him all of 5 seconds to see it. http://www.soursound.com Great guy.

I hard wired it. I thought about doing the socket, but just went with the cord available at Antique Radio Supply. Glad to hear parts are on the way. Look forward to seeing how it turns out. Good luck!
Hey Brendan,

I'm guessing you're a PDXer like myself. Glad you found Brian, 'cuz he's a superb amp tech. He's incredibly knowledgeable and does great work on all kinds of electronics. He's the only guy in town worth trusting with keyboards too. I've heard that his buddy at Leighton Audio is also tops for tube amps, but that he's more expensive. Glad the masterful CJ was able to help you out with your Guild.
 
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Well I'm finally back after a little hiatus. I updated the schematic back on page 4.

All of my parts came in last week. I fired up the iron this weekend and went after it. First thing I had to do was modify the 3PDT switches. I drilled and tapped new 4-40 threads into them to match up to the existing chassis holes. All of the tubular caps were replaced as well as some of the ceramic discs. I used the Orange Drops for most, but for my own amps I use Xicon, CDE or Nichoson. I found the OD to be fairly large compared to the others so I most likely won't be using them by choice next time.

The first capacitor on the input power supply was a 50uF, which I found out after pulling it. When I was reading the original schematics, I thought it was a 30, so I bought a 33uF to go there. I've ordered a 47uF to replace it, and that should be here by week's end.

I replaced the power cord with a 3 prong one that I had extra. Snipped the end of it and soldered it in. When I first plugged the amp's power cord in, I noticed the power on light was lit. Figured out that the original switch I replaced operated its contacts opposite of the new switch. A quick swap of the throws fixed that.

I changed the rear jacks to be speaker out jacks per the amp owner's request. I actually like that much better.

There was a bit of hum when I first powered it up. Tweaking the hum balance pot eliminated it. Probing the tube sockets revealed a bad solder joint and stray wires for V3-6. The OT leads were also touching pin 5 occasionally, especially when I probed it. Wasn't a pretty sight or sound. Fixed that and no more issues there.

The volume pot works fine on the low end, produces some very nasty distortion in the middle, and has some creamy overdrive at the high end. I cleaned all the pots, but this pot just doesn't seem to want to clean up. Now I need to find a replacement that has a switch on it. Any recommendations? The value I measured across the leads was 85k audio taper, so I'm assuming it was/is an A100k pot, yes? Bass pot worked ok, measured A1M. Treble pot worked ok, measured A3.8M.

Trem circuit didn't work at first. Turns out the 3PDT switch has one of the throws not working. When I grounded the Trem speed pot, the tremolo worked nice. It has some decent speed adjustment, but it doesn't get as slow as I would like. Slowest is around 1/2 second, maybe a little longer than that. That pot measured A2.3M. Depth worked good. No thumping out of it until the last 10% of turn. Then I could only hear it when I didn't play anything. Otherwise, it was unnoticeable while playing.

So, later this week, I'll replace the trem on/off switch and install the 47uF cap on the first filter stage. Any ideas what the nominal values of pots should be? I may replace all of them, but I at least want to get the schematic correct. Got a lead on where to find the correct volume pot?

Thanks!

Here are a couple quick pix of the amp.

Guildcompleteoverview.jpg


Guildcompletefirststagefilter.jpg


Guildcompletebiascircuit.jpg
 

capnjuan

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Hi Mike; nice fix on the switch body ... the FMIC schematic IDs the volume pot as 100K ... that's the one with the switchable 'Bright' function on the funky linkage? The bass and treble pots are ID'd as 3 meg but I don't think the values of either are critical. Doug Hoffman / Hoffman Amps carries 10K/audio and 1 meg/audio pots with pull on/push off contacts on the back listed here. T'were mine, I'd use the 1megA pot. Good luck; looks like you have the amp back on the road again! J
 
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I finally got the new pots in late last week and started back into the amp. I ended up ordering 2M pots from Weber, as well as the 1M audio push-pull for the volume/bright control. I couldn't find any 3M pots so settled on the 2M. First issue was that they did not have any of the values in knurled shafts. Second issue with those were that the 2M pots came with 1/4" shafts and not 6mm shafts as advertised. The nuts and washers that were provided to mount those didn't fit either as those were for 6mm. Luckily I had spare hardware laying around so I was able to use them. I had some spare 6mm knobs to put on, but they only fit on the volume control. The owner will be deciding what type of knobs he wants and then I'll get them installed.

I had some high pitched squeal/repetitive popping sounds that occurred when I had the volume all the way up. Turning the treble pot changed the speed and pitch of the sounds. Turned out to be one of the ceramic disc caps on the treble pot that I didn't initially replace. I replaced both of those with some polys.

I also had to replace the signal wires from the volume pot and from the tremolo pot. I used some shielded pairs that I had in my box of stuff.

The volume when the tremolo was turned on seemed a bit lower than when off. I increased R34 to 1.5M to fix this.

The two switches on the volume pot were two SPST. The original volume pot had one NC and one NO SPST. So I decided to just switch the cap in parallel with R15 instead of switching an RC network in and out. This also eliminated the volume drop when pulling the bright knob as the resistor is in the circuit all the time.

I was overdriving V2b with the bass knob up a bit so I lowered C13. I also paralleled a 1M resistor across the volume pot to reduce the signal going into the V2b stage. Both of these seemed to fix the problem. I also had R16 shown connected to the wrong location on my previous schematic versions and fixed that.

I experimented with R33 as a 22k resistor to increase the gain. That worked beautifully, but decided to go back to the 10k as it required turning down the guitar volume a bit too far to clean up the signal. The high gain channel gives enough grit. I didn't try that input with single coils, though, but expect nice results.

Now the amp works well. I can dime the volume and get some really nice grit out of it. Then, turning back the volume knob on my guitar cleans it up. Switching from humbuckers to single coil mode produces a beautiful clean. Overall, this was a fun amp to work on. I'm quite pleased with the results I was able to produce.

The original schematic is updated and located back on page 4 still.

And now for the schematic and pictures of the completed amp as I have modified it.
GuildThunder1sheet1Rev20.jpg


GuildThunder1sheet2Rev20.jpg


Guilddoneoverview.jpg


Guilddoneinternal1.jpg


Guilddoneinputpowersection.jpg


Guilddonerectifiersection.jpg


Guilddonepreampsection.jpg


Guilddonetonestacksection.jpg


Guilddonevolumesection.jpg


Guilddonetremsection.jpg


Guilddonepowerampsection.jpg


Thanks for looking!
 

capnjuan

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Congratulations Mike; well thought-out fixes and fix-'em-ups! :) CJ
 

capnjuan

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Brendan said:
... The tremolo still works, but the depth pot (hidden at the back of the chassis) can only move to half of its range before the thump comes on. I can make it faster or slower by spinning the speed pot at the control panel. It has a fair amount of depth before thump right now, but I was hoping to get a bit more range on the depth.
Hi Brendan; if you're still following this thread, this is a pretty good explanation of how a trem function like yours works; might help, might not. Best wishes, John

http://archive.ampage.org/threads/5/gagd/296669/Fender_mods-2.html
 

Brendan

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capnjuan said:
Brendan said:
... The tremolo still works, but the depth pot (hidden at the back of the chassis) can only move to half of its range before the thump comes on. I can make it faster or slower by spinning the speed pot at the control panel. It has a fair amount of depth before thump right now, but I was hoping to get a bit more range on the depth.
Hi Brendan; if you're still following this thread, this is a pretty good explanation of how a trem function like yours works; might help, might not. Best wishes, John

http://archive.ampage.org/threads/5/gagd/296669/Fender_mods-2.html

Wow, thanks John. I have a few spare diodes around. Is the wiper lug the one in the center?
 

capnjuan

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somecallmetim

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Howdy & Merry Christmas!

I'm just bumping this thread up, because I scored a nice t-1-12 on the bay. It looks identical to the one in the first post. It's a bit crackely & cuts out when I turn the trem on, she'll get a proper cleaning & then Caps & 3prong. Pics coming soon.

-tim
 

capnjuan

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Hi Tim and belated congratulations on your new amp. Is this it: closed eBay auction link? Looking forward to some pics; the first amp in this thread is the later version; 'ears' are gone from the upper/front cabinet side panels ... present on the linked auction amp ... and there are some other bits and pieces. Anyway, congrats again - pics please if/when you get the chance.
 

somecallmetim

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Happy New Year!

That is indeed mine. It felt like a bit of a gamble buying a vintage amp from isoldit... I am shocked at the prices the Guild amps often bring. Last week another one went for similar money...

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 255wt_1141

...I might have bought it too, but fixed the brakes on my truck instead.


Anyhow, a little contact cleaner everywhere cured the trem problem & general crackelyness, though It also has a touch of thump with the trem on...



DSCF1437.jpg


The Serial # is 2363
Speaker codes 137 433 Making it a CTS from the 33rd week of 1964...

DSCF1438.jpg



The power & rectifier tubes are the original Guilds, made in West Germany. It came with a Raython 7025 & E-H 12ax7 in the preamp slots.

DSCF1442.jpg


A nice clean unmolested chassis...

DSCF1443.jpg


There is a little bit of goo coming out of the bypass caps. I have some 25/25s on hand, I probably should wait to change them until I get the proper 32uf caps...

DSCF1445.jpg


I
 

somecallmetim

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One other thing. I'd like to replace the grill cloth. AES dosent seem to have anything like it, Any where else to look?
 

capnjuan

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Hi Tim; our member matsickma dubbed that grill the 'fishscale' grill. No; not available in the aftermarket and, if you haven't found out by now, it'll be pretty badly oxidized, lost its flexibility, and if you rub your hand on it, you'll pick up little bits of plastic that will go right into your skin like fiberglass, steel wool ... or fishscales :(

The 32uf bypass cap is not widely supported anymore; the Sprague or any equivalent 25uf/25v is the way to go. You won't hear any difference and the bias/gain implications are negligible. You don't have a pair of 'brown' taps on the power transformer and there's that big, blue cap near the output tubes making your amp cathode- not fixed-bias. As long as your in the mood to upgrade bypass caps, don't forget that one.

Finally the thumpy trem: if you wander through this entire thread, you'll find three different trem arrangements. As I've recently had an adverse electronic event, my cache of Guild schematics is gone ... In the T1 RVT amps, they used one of the triode sections of one of the output tubes for the trem oscillator and I don't remember whether that's the case with the T1s or not but there are typically 3 trem caps that are tremming whether you have the trem function engaged or not making them the usual suspects.

In any event, Congratulations! I love those red stickers on the speakers ... I also note yours has all the knobs where the other one didn't.
 
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