Wonderland/JM100 build
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- martin manning
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Re: Wonderland/JM100 build
Which 68k did you increase to 100k? Is it the one in the 1M/68k divider?
- norburybrook
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Re: Wonderland/JM100 build
yes.
I've ben talking with jelle on the amp builders facebook page and he says the pictures of the JM amp don't show 1M-68K , he recons to try 180k into 68K.
need to sort this hum out first.
bugger!!!!
Marcus
I've ben talking with jelle on the amp builders facebook page and he says the pictures of the JM amp don't show 1M-68K , he recons to try 180k into 68K.
need to sort this hum out first.
bugger!!!!
Marcus
- pompeiisneaks
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Re: RE: Re: Wonderland/JM100 build
Yeah we need to convince jelle to get back on here more often. I see him all the time on fb as wellnorburybrook wrote:yes.
I've ben talking with jelle on the amp builders facebook page and he says the pictures of the JM amp don't show 1M-68K , he recons to try 180k into 68K.
need to sort this hum out first.
bugger!!!!
Marcus
Sent from my LG-V521 using Tapatalk
tUber Nerd!
Re: Wonderland/JM100 build
ouch,. now there is an argument for a fuse on that secondary HT? better check them diodes!
- norburybrook
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Re: Wonderland/JM100 build
Dave,Martin
I've done every combination of the valves and it's still the same hum.So can I assume that the valves are fine?
the amp sounds great, voltages are still all good, I presume then that the diodes are fine.
Ok, here's a weird one. the heater string is now showing 6vAC on one side and 0 on the other. I'm sure it was 3 and 3 when I checked
could that be a pointer?
Marcus
- martin manning
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Re: Wonderland/JM100 build
What are filament voltages with all valves (including preamp) removed?
Last edited by martin manning on Fri Apr 21, 2017 2:57 pm, edited 1 time in total.
Re: Wonderland/JM100 build
that would cause hum for sure, one side of the heaters is grounded or shorted,.
- norburybrook
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Re: Wonderland/JM100 build
same, 6 on one side 0 on the other
M
M
- martin manning
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Re: Wonderland/JM100 build
Disconnect the PT filament leads and measure at the source. Also measure resistance to ground from each side of the filament wiring and verify 100R.
- norburybrook
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Re: Wonderland/JM100 build
there 6 vAC between the secondary's.
each side of the filament is 100R
M
each side of the filament is 100R
M
- martin manning
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Re: Wonderland/JM100 build
That's good news. Reconnect the PT leads and put valves back in one at a time and check voltage from each side to ground.
- norburybrook
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Re: Wonderland/JM100 build
1st 6l6 I put in measured 6 and 0
M
M
- martin manning
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Re: Wonderland/JM100 build
Try a 6L6 from another amp. Is it back to 3V each side with no valves in?
- pompeiisneaks
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Re: RE: Re: Wonderland/JM100 build
It depends on how you measure the voltage. If you measure from ground each leg is 3 volts. If you measure leg to leg you're going to get 6.3 if you accidentally measure leg to the same leg you're getting 0vnorburybrook wrote:Dave,Martin
I've done every combination of the valves and it's still the same hum.So can I assume that the valves are fine?
the amp sounds great, voltages are still all good, I presume then that the diodes are fine.
Ok, here's a weird one. the heater string is now showing 6vAC on one side and 0 on the other. I'm sure it was 3 and 3 when I checked
could that be a pointer?
Marcus
Sent from my LG-V521 using Tapatalk
tUber Nerd!
- norburybrook
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Re: Wonderland/JM100 build
No it's 6 and 0 with no valves in.martin manning wrote: ↑Fri Apr 21, 2017 3:25 pm Try a 6L6 from another amp. Is it back to 3V each side with no valves in?
M