102 type build to commence...

Overdrive Special, Steel String Singer, Dumbleland, Odyssey, Winterland, etc. -
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martin manning
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Re: 102 type build to commence...

Post by martin manning »

Cheap, too: One $3 pot replaces a jack and a trimmer! You will need a bushing of some sort. Try putting an o-ring around the pot's bushing to center it in the 3/8" hole.
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Mr. dB
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Re: 102 type build to commence...

Post by Mr. dB »

martin manning wrote: Fri Aug 18, 2017 10:30 am Another option is replace the FET jack with a pull pot that switches the FET in, and replaces the trimmer on the FET board.
https://www.amplifiedparts.com/products ... mm-bushing
Or a relay, footswitchable...
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stelligan
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a snails pace...

Post by stelligan »

Chugging away on the build. Most of the power section is wired now and will be moving on to the preamp. Still some parts to come but not many. I've been making a list and hoping to source them from one vendor(which is proving problematic).

Oh, and I think I found all the parts for the FET(fukkin' electronic thang) in the parts drawer!!
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stelligan
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Re: 102 type build to commence...

Post by stelligan »

A kitchen remodel can really put a crimp in yer amp building style. Finally back at this after getting all too intimate with table saws, nail guns, paint sprayers, tile saws......
Kitchen still ain't buttoned up, but a guy has to have some fun.

Power up is likely next week. Still to do: pedal jack wiring, preamp/power amp jack treble reducing caps and heaters.

Don't ask me why I flew the shielded OD lead over top of the board...

Thanks to Aaron(aflynt) for the layout: http://ampgarage.com/forum/download/file.php?id=23252


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stelligan
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It's alive!! Sorta. Trouble shooting begins....

Post by stelligan »

Power up yesterday went OK... Quiet as a mouse - no smoke. Voltages were spot on except bias section. Could only adjust to 26ma.
Power tube plates were reading 450V
B+3 439
B+4 328
B+5 320
This was with a crappy quad of EH 6L6 that I used to power up.
Swapped a 22K resistor in at bias pot and now great range for adjusting. *Do I need to change the 3K3 in the bias supply to get Power tube plate voltages back up?

Put Winged C 6L6s in today. Cleans are gloriously good.

voltages are now:
Power tubes 422V on plates biased at approx 32ma.
B+3 412
B+4 317
B+5 309
V2 211 & 207
V1 192 & 188

Now for the bad....
Seems to be a problem with the OD, Rock/Jazz and PAB. When OD is switched on - little to no audio. Can hear increases in what little volume that passes when cranking the gain and level pots. Also - PAB works with Rock/Jazz in jazz position, but seems to have no effect in Rock position.

The layout I am going from is referenced above. Any help is greatly appreciated!!

I am sure I am missing some little fricking thing. :?
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martin manning
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Re: 102 type build to commence...

Post by martin manning »

Power tube bias is a bit cool: (422V x 32 mA)/30W = 45%, including screen current. I'd increase the idle current to (60% x 30W)/422V = 43 mA and see where you land, shooting for 55-60%. Re the loss of signal in OD, sounds like some signal tracing is in order...
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stelligan
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Re: 102 type build to commence...

Post by stelligan »

martin manning wrote: Sat May 19, 2018 12:15 pm Power tube bias is a bit cool: (422V x 32 mA)/30W = 45%, including screen current. I'd increase the idle current to (60% x 30W)/422V = 43 mA and see where you land, shooting for 55-60%. Re the loss of signal in OD, sounds like some signal tracing is in order...
Thanks Martin.

Yeah, I am going to bypass the relays with a clip lead and just go straight in to the OD to see if there is sound. Will crank the bias per your recommendation. Is it worthwhile to play with the dropping string to bring V1 voltages up a hair?

Thanks, man!
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martin manning
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Re: 102 type build to commence...

Post by martin manning »

Plate voltage is what it is, depending a bit on how hot you bias. I start with the standard dropping resistors, and adjust the first one (2k7 in Tony's layout) to get around 185V +/- on the V1 plates... So, you look good now, but it might drop a bit when you turn up the idle current.
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stelligan
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Re: 102 type build to commence...

Post by stelligan »

Well, after cranking up the bias per Martin's recommendation, cleans are even gooder and V1 voltage is pretty much the same. Bypassed the relay with a clip lead an - VOILA! We have overdrive. By the truckload. Very excited to near the finish line on this build. Thanks to all for the help. Will post clips once I get all the relay and PAB nonsense sorted....
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stelligan
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It's Alive!! Really, this time....

Post by stelligan »

Problems solved!!

Bottom 2 legs of PAB switch not jumpered and 1 contact of OD relay was not jumpered.

Really fun amp. Treble pot does not seem to do much in rock mode. Maybe a problem there? Otherwise, lots o' fun ahead!! :D

** couldn't make noise in the house much today but, here's a taste of what the amp can do silently.... Straight into computer from a reactive load(Torpedo Captor). Speaker IRs no EQ. Strat neck pickup on left - clean. Strat bridge on right - OD + PAB. Reverb added to clean & echo added to OD.
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pompeiisneaks
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Re: 102 type build to commence...

Post by pompeiisneaks »

Sounds excellent! I edited your post to use the MP3 link instead so people can just play it inline (you just have to right click on the link to the attachment, paste that in, and then highlight it and click the 'mp3' button on top and it surrounds it with mp3 tags to make it inline.)

~Phil
tUber Nerd!
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Mr. dB
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Re: It's Alive!! Really, this time....

Post by Mr. dB »

stelligan wrote: Sun May 20, 2018 7:56 pm Problems solved!!

Bottom 2 legs of PAB switch not jumpered and 1 contact of OD relay was not jumpered.

Really fun amp. Treble pot does not seem to do much in rock mode. Maybe a problem there? Otherwise, lots o' fun ahead!! :D

** couldn't make noise in the house much today but, here's a taste of what the amp can do silently.... Straight into computer from a reactive load(Torpedo Captor). Speaker IRs no EQ. Strat neck pickup on left - clean. Strat bridge on right - OD + PAB. Reverb added to clean & echo added to OD.
That turned out well.
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stelligan
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Re: It's Alive!! Really, this time....

Post by stelligan »

Mr. dB wrote: Mon May 21, 2018 10:13 pm That turned out well.
Thanks for checking it out Mr. db. Was well worth the effort, I must say. More gain with a Strat than I would ever need and without an FET(I know, I'm lazy...). And just wild with a 345 and Tele.

You started your build?
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martin manning
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Re: 102 type build to commence...

Post by martin manning »

Some nice overdrive tones there, and the Two Notes load box doesn't seem to be intrusive at all. On the treble control issue, a quick check would be to see if the bottom of the treble pot is connected directly to the top of the bass pot in Rock mode.
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stelligan
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Re: 102 type build to commence...

Post by stelligan »

martin manning wrote: Tue May 22, 2018 10:00 am Some nice overdrive tones there, and the Two Notes load box doesn't seem to be intrusive at all. On the treble control issue, a quick check would be to see if the bottom of the treble pot is connected directly to the top of the bass pot in Rock mode.
Thanks so much for all the help, Martin!

Will check when I move it from it's temporary home(combo) into a head cab. I had just heard that this amp was notoriously bright and it is not striking me that way at all. Treble is at 2 o'clock, mid at noon, bass at 10 o'clock. It's not that the pot is doing nothing - just extremely subtle. I do have a treble reducing network at the loop. I may bypass that with a short jumper cable. Have played it through EVM 12L open back, 2 x G1265 and in this combo cab with an Eminence Hemp Dog. Will admit, it is the first time I have used that speaker. I rather like it. Not that much darker than my 12Ls.
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