1086 gain mods?

[Graham Pearson]

I haven't done a gain mod to the 1086, but the mid-shift caps are right behind the small toggle. C14, C15, I believe.

The above message is the third on page 1 of this topic.

I checked my 1086 and the caps immediately behind the Mid-Shift toggle are C5 and C14. BUT ON MY 1086, THESE CAPS HAVE IDENTICAL VALUES - 250p. ALSO, I DON'T HEAR ANY DIFFERENCE IN TONE WHEN I TOGGLE THE MID-SHIFT.

Before I go dissasembling my 1086 to find out which caps are switched in and out by the mid-shift switch, does anyone know for sure?

 

[SacredGroove]

I haven't done a gain mod to the 1086, but the mid-shift caps are right behind the small toggle. C14, C15, I believe.

The above message is the third on page 1 of this topic.

I checked my 1086 and the caps immediately behind the Mid-Shift toggle are C5 and C14. BUT ON MY 1086, THESE CAPS HAVE IDENTICAL VALUES - 250p. ALSO, I DON'T HEAR ANY DIFFERENCE IN TONE WHEN I TOGGLE THE MID-SHIFT.

Before I go dissasembling my 1086 to find out which caps are switched in and out by the mid-shift switch, does anyone know for sure?

C5 is C15 on most other boards it seems. Yes, C14 and C5 are the treble caps. I don't know why you're not hearing a difference switching between them. Bad switch, broken trace, bad cap? Regardless of the cap values, there should be a shift when the second cap is added to the circuit. The caps are in series, so when the second cap, C5, is activated (added to C14) the tone will become more scooped than the first cap, C14, by itself.

FWIW, series capacitance calculates like parallel resistance. CT=1/ 1/C1+1/C2+1/C3...Cn. The reciprocal of the sum of reciprocals.

 

[Graham Pearson]

S/G:
Thanks for the clarification. I didn't realize the capacitors were in series. I assumed the switch toggled either one or the other into the circuit. I'll check the toggle switch / 250p capacitors / my hearing aid.

 

[Graham Pearson]

My previous posts refer to caps having values of 250p in my 1086 at C5 and C14 positions. Another topic on this forum talks about 250p caps in these positions on other modules:
http://mtsforum.grailtone.com/viewtopic.php?t=4278&postdays=0&postorder=asc&start=19

However, I'm mistaken, both my caps are marked 250K which is surely 25p not 250p. I wonder what these cap values should be? I'm asking because I still don't hear any difference in tone when toggling the Mid-Voicing switch on my 1086.

 

[SacredGroove]

However, I'm mistaken, both my caps are marked 250K which is surely 25p not 250p. I wonder what these cap values should be? I'm asking because I still don't hear any difference in tone when toggling the Mid-Voicing switch on my 1086.

Are you sure they don't say 251k? I know a 0 doesn't look like a 1, but you never know. :wink:

Does the current tone sound severely scooped? If you indeed have 25pF caps then my guess is that you probably won't hear much of a difference, if any at all, since there is only 12.5pF difference when one is switched in/out.

 

[Graham Pearson]

I just verified that the markings on each of the orange-drop capacitors are:
250K / 1kV / 8

The soldering on each of these capacitors looks identical to that on all of the other components. Nothing suggests that these capacitors have been modded. Perhaps this was a manufacturing oversight?

Also, the tone DOES sound extremely scooped, which suggests that the caps are really 25p rather than 250p.

 

[Graham Pearson]

Rob, our in-house Jaded Faith modding guru and master of reading tea-leaves, capacitor and resistor values, just informed me that the 2 orange-drop capacitors I have been fretting about in my 1086 are indeed correct.

For some reason, these caps are incorrectly labeled 250K (25p). The correct labeling should be 251K (250p). So if you see orange-drop caps in your modules with the label "250K / 1kV / B", read them as 250p.

 

[SacredGroove]

Orange drops under 1000pF? :shock:
If you in fact have 250pF caps in both, C14 and C5, you should hear a definitive difference in tone when you switch between the mid-voice modes.

 

[Bert 690]

I just got a 1086 module today, and the caps say 271 then 1KV underneath. What does that mean?

I also am not hearing any difference when I flip the mid switch. The module was used but it does not appear modded.

 

[Jaded Faith]

They aren't Orange Drops, they are Sprague ceramics dipped in a similar coating to Orange Drops. The look is very similar.