I used a layout from Ceriatone (not sure). I don't want to post it here because of copyright issues. In the #124 Layout B+3 is grounded along with B+2 to ground No. 2. The question is, if the PI is on the preamp or the power amp side.
I'll take a note, and change this, if there are any ground loop issues when it comes to testing.
Thanks!
Cheers
Gerhard
Sorry had to laugh a little at the copyright issue concern. Ceriatone got the layout from this site and I don't think they care much about copyright, trademark, or any other rights.
CW
norburybrook wrote: ↑Mon Nov 11, 2019 10:00 pmthe filter cap that supplies the FET board and V1 is grounded at the input, the other 3 are grounded together at the output tubes, called ground 2 on the layout.
I see it like this:
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norburybrook wrote: ↑Mon Nov 11, 2019 10:00 pmthe filter cap that supplies the FET board and V1 is grounded at the input, the other 3 are grounded together at the output tubes, called ground 2 on the layout.
I see it like this:
I was going from the #124 in our files section.
124 low plate classic rev1.jpg
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erwin_ve wrote: ↑Mon Nov 11, 2019 4:02 pm
You might reconsider the grounding of your capacitors; check the #124 layout.
Erwin, are you thinking about the PI cap going with the preamp caps? The eyelet board layout intentionally matches the grounding on the JBorders PCB. I would agree that the PI node filter ground might better be split out and grounded at the rear of the chassis along with the PI ground, but I know from personal experience that it produces a very quiet result as shown. That JBorders PCB is shown in the 183 layout.
Sluckey's point about hooking separate jumpers into each eyelet is well taken.
Martin,
Yes that was the case; When grounding the PI cathode/NFB at the loop jacks why would you ground the B3+cap (for the PI) at the input? Makes no sense imo.
Your experience and others it will be hum free and I'm 100% sure that is the case.
norburybrook wrote: ↑Tue Nov 12, 2019 9:19 amI was going from the #124 in our files section.
Marcus, in the layout it's the same as the schematic shows: FET filter, V1 filter (in back corner), and V2 filter (2x 10u can at the front) all ground at the input. Pi filter and screen filter eyelets are tied together and ground at the output tubes.
I still wait for a 500k OD trimmer. Or, I have a 500k pot on hand, so I can use this instead of the impedance selector as the OD trimmer.
One thing I feel a bit insecure, is the 330pf Mica cap before the treble pot. I've ordered 5, but all of them show around 250-270 pF on my multimeter. I picked the 270 pF an soldered it in.
Should I go with the 0.002 uF, as it is in the Skyline tone stack?
Ok, these questions will come later. First of all, get the baby on it's feet to run...
Cheers
Gerhard
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Lothy wrote: ↑Sun Nov 17, 2019 6:29 pmI still wait for a 500k OD trimmer. Or, I have a 500k pot on hand, so I can use this instead of the impedance selector as the OD trimmer.
#124 is a bit of an odd duck there. Other ODS' documented here use a 100k trimmer.
Lothy wrote: ↑Sun Nov 17, 2019 6:29 pmOne thing I feel a bit insecure, is the 330pf Mica cap before the treble pot. I've ordered 5, but all of them show around 250-270 pF on my multimeter. I picked the 270 pF an soldered it in. Should I go with the 0.002 uF, as it is in the Skyline tone stack?
Wow, if that's accurate they're more than 20% out... What's the marked tolerance on those caps? I am using a 370p and a 2n for the treble/mid boost caps in my 124-ish amp, other Skyline amps use 390p for the treble.
Lothy wrote: ↑Sun Nov 17, 2019 6:29 pmI still wait for a 500k OD trimmer. Or, I have a 500k pot on hand, so I can use this instead of the impedance selector as the OD trimmer.
#124 is a bit of an odd duck there. Other ODS' documented here use a 100k trimmer.
Lothy wrote: ↑Sun Nov 17, 2019 6:29 pmOne thing I feel a bit insecure, is the 330pf Mica cap before the treble pot. I've ordered 5, but all of them show around 250-270 pF on my multimeter. I picked the 270 pF an soldered it in. Should I go with the 0.002 uF, as it is in the Skyline tone stack?
Wow, if that's accurate they're more than 20% out... What's the marked tolerance on those caps? I am using a 370p and a 2n for the treble/mid boost caps in my 124-ish amp, other Skyline amps use 390p for the treble.
Also realize that measuring that low of capacitance with almost all multimeters isn't going to be very accurate, you need super short leads and a more carefully designed circuit to measure in the pF range.
