Hotrod Bassman50 do-up

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Re: Hotrod Bassman50 do-up

Post by Cdog »

Very tidy indeed!
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Re: Hotrod Bassman50 do-up

Post by jeremyb »

Hmmmm, anyone else unable to see the attachments?
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Re: Hotrod Bassman50 do-up

Post by calling card »

Yeah me too, if I open in another tab says quicktime needs update, not done so yet.
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Re: Hotrod Bassman50 do-up

Post by tubeswell »

'61 bassman (6G6B) normal channel wired in, bass channel partly wired in
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Re: Hotrod Bassman50 do-up

Post by elams1894 »

Thats looks cool! Nice and neat layout and I'm digging the Mustards. I have quite a few of them too which I'm keen to use in a little amp. I'm really looking fwd to hearing her sound. Good stuff!
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Re: Hotrod Bassman50 do-up

Post by Slowy »

jeremyb wrote:Hmmmm, anyone else unable to see the attachments?
Mine says, " Not a JPEG file. Starts with 0x00 0x00 "

That make sense to you Technoninjas?
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Re: Hotrod Bassman50 do-up

Post by Cdog »

Now that you mention it, I can only see one picture, didn't realize there were others at first... Hmmm
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Re: Hotrod Bassman50 do-up

Post by tubeswell »

Finished wiring up V1 just now

Sorry about the attachments everyone. I can't reduce the size of the jpg files to under 100k (smallest I can get to is about 280k) so I have to change the format to jp2 and then reduce it to 56k and then swap the last part of the filename back to 'jpg' to get the images to load up here. I've given up on using flickr to load my photos to.
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Last edited by tubeswell on Fri Jan 23, 2015 1:37 pm, edited 1 time in total.
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Re: Hotrod Bassman50 do-up

Post by tubeswell »

elams1894 wrote:Thats looks cool! Nice and neat layout and I'm digging the Mustards. I have quite a few of them too which I'm keen to use in a little amp. I'm really looking fwd to hearing her sound. Good stuff!
I'm 6 mustards short of having them throughout dammit. (I need two each of 0.1uF, 0.01uF, 0.25uF)
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Re: Hotrod Bassman50 do-up

Post by Anvil Amps Alan »

Ok, I will take the hint.
Got 'em.
Would 0.22 400v do?
I have a lot of 125v mustards but not so many 400v.
PM me.
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Re: Hotrod Bassman50 do-up

Post by StrummersOfThunder »

Looking great man, nice n neat.
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Re: Hotrod Bassman50 do-up

Post by tubeswell »

Anvil Amps Alan wrote:Ok, I will take the hint.
Got 'em.
Would 0.22 400v do?
I have a lot of 125v mustards but not so many 400v.
PM me.
Thanks Alan - I've already got heaps of 22nF 400V in my stash. Its the other ones I'm short of
Last edited by tubeswell on Sat Jan 24, 2015 9:11 am, edited 1 time in total.
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Re: Hotrod Bassman50 do-up

Post by tubeswell »

That old Jansen PT has great regulation. Unloaded B+ was 695. With EL34s (and all the pre-amp toobs) loaded, the B+ is sitting at 613. Screens are around 512 through that 4k7 dropper node (21.5mA going through that resistor). Methinks them screens need to come down quite a bit. I've got heaps of 10W resistors but nothing in 15k-ish. I'll check out my favourite electrical wholesaler.
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Re: Hotrod Bassman50 do-up

Post by Anvil Amps Alan »

tubeswell wrote:
Anvil Amps Alan wrote:Ok, I will take the hint.
Got 'em.
Would 0.22 400v do?
I have a lot of 125v mustards but not so many 400v.
PM me.
Thanks Alan - I've already got heaps of 22nF 400V in my stash. Its the other ones I'm short of
I can send you the 4 others.( .01, 0.1)
Let me know where.
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Re: Hotrod Bassman50 do-up

Post by tubeswell »

Results running 2 x EL34s:

B+ 617 (655 on std-by)
Heater elevation 53V
Plates 616V @ 28.4mA
Screens 380V (I increased the screen dropper to 15k)
Grids -34V
Suppressors -24V (pinned to Bias supply)

I ran a pair of JJEL34 continuously for 4 hours this way with no bad results so far FWIW. (touch wood)

PI supply node 346V
Normal Ch supply node 324V
Bass Ch supply node 236V
CF (V1b cathode) 133V

FWIW I discovered that the trouble with the 6G6B preamp is that the Bass Channel is prone to self-oscillation when the vol pot is about 2/3 of maximum rotation if built as per the schematic. I found that this was able to be cured by putting a coupling cap between the CF cathode and the junction of the 1M/250pF (I used 22nF with good results). There you go
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