Jamesemt Posted February 5 Share Posted February 5 So my modified Sadowsky Jazz has an early 80s Precision Special preamp which I absolutely love and had fitted about 10 years ago. The bass and treble pots have lost their indent, making them feel very worn, and I would like to replace them. I have a local electronics company that will do the work if I can source the pots...can anyone help with identifying them or modern replacements that will fit? They are mounted direct to the board. The company suggested replacing the entire board but I know they are like hen's teeth anyway now, and I could be in a similar position... Any advice? I really like the preamp and don't want to change it if possible. It was suggested years ago that I could get the circuit cloned... But who would do that for me? I also have an ACG that I would like to fit similar to. Thanks. Quote Link to comment Share on other sites More sharing options...
ahpook Posted February 5 Share Posted February 5 (edited) There's some info and a circuit diagram here... Does that preamp look like yours ? If you can post some pics then I'm sure the Basschat Flux Sniffin' Crew will be able to help. Edited February 5 by ahpook Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 5 Author Share Posted February 5 Yeah thanks I've seen that schematic before... And tbh I don't know what I'm looking at 😂 I *think* it's right. Here are some awful photos as its a bit crammed in! Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 5 Author Share Posted February 5 Quote Link to comment Share on other sites More sharing options...
itu Posted February 5 Share Posted February 5 The centre detents can be most probably fixed by opening the pots and doing certain mechanical actions. Not rocket science, nor music theory. If I did it, I probably wouldn't solder the pots if not necessary. The excessive heat is something pots do not like. Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 5 Author Share Posted February 5 23 minutes ago, itu said: The centre detents can be most probably fixed by opening the pots and doing certain mechanical actions. Not rocket science, nor music theory. If I did it, I probably wouldn't solder the pots if not necessary. The excessive heat is something pots do not like. Thanks - the electronics guy didn't suggest that so I probably can't use him. Quote Link to comment Share on other sites More sharing options...
BlueMoon Posted February 6 Share Posted February 6 It looks to me like the Fender active circuit has been modified prior to fitting to your Sadowsky, since the pots of the original circuit were soldered to the board (see example pic). In your last pic above I do not see that any pots are on the board, so changing the pots should not be a major exercise if you can locate the correct potentiometers. Am I missing something? Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 6 Author Share Posted February 6 Ah sorry. Yes I got John East to alter the preamp so it would fit my Jazz Sadowsky but never actually saw the preamp beforehand as it was sent straight to him! So can anyone identify the pots for me? Quote Link to comment Share on other sites More sharing options...
BlueMoon Posted February 6 Share Posted February 6 No apology necessary. If John has done the work then you know it was done properly. Details of the original Fender parts attached below. The tandem pot will be tricky to source, the others appear to be industry standard. 1 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 6 Share Posted February 6 (edited) 1 hour ago, Jamesemt said: ... I got John East to alter the preamp so it would fit my Jazz Sadowsky but never actually saw the preamp beforehand as it was sent straight to him! So can anyone identify the pots for me? From the board/schematic, the pots are all 250K ohms, linear** taper with centre detent, apart from the Vol pot which is audio taper (no detent). The Tone pot is a double unit (mentioned above) eg. a 2 track, single-shaft blend pot. You'd need to remove the control knobs to check whether they require split or solid shafts (or can tighten onto either shaft type) (**The schematic shows the Passive Tone control as "Aud" but i suspect this is a typo! - a Vol blend control might be 2x Audio taper, 1 in reverse, but Tone controls are usually Linear) Google "guitar 250k linear potentiometer detent" and you'll see some likely sources - watch out for hidden Packing/Delivery/Minimum-order costs HTH [Edit: Oops - post crossed with Blue Moon ...i did refresh to check b4 posting!) Edited February 6 by sandy_r 1 Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 7 Author Share Posted February 7 (edited) OK thanks. Would a "dual deck blend/balance" work for the twin pot? Like this: https://www.ebay.co.uk/itm/275309543988?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=kgixFco9Qma&sssrc=4429486&ssuid=vNO_rdY8SEe&var=575584568920&widget_ver=artemis&media=COPY Obvs need to check the shaft type. Edited February 7 by Jamesemt Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 7 Share Posted February 7 (edited) 39 minutes ago, Jamesemt said: ... Would a "dual deck blend/balance" work for the twin pot? Like this: https://www.ebay.co.uk/itm/275309543988?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=kgixFco9Qma&sssrc=4429486&ssuid=vNO_rdY8SEe&var=575584568920&widget_ver=artemis&media=COPY Obvs need to check the shaft type. That pot has at least 1 difference to the schematic/diagram - possibly two... firstly it has 2 concentric shafts and needs 2 'stacked' type control knobs - do you have suitably matching ones? Do you want a stacked control? secondly, this may be an Audio blend, not a Linear one - the schematic states Linear taper for the Active Treble half (and confusingly Audio taper for the Passive Treble half ...but i strongly suspect this is a typo! Active Tone controls are usually Linear, and i'm not aware that you can buy mixed taper types on a blend pot) If you're happy to have a stacked control, and can get suitable knobs for it, you could message the seller and ask which taper type it is - if it is definitely Linear then electrically it will do what is required HTH [Edit: this would be a closer match to the spec - 250k Linear Blend Pot ...assuming the shaft suits the existing control knob] Edited February 7 by sandy_r Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 7 Author Share Posted February 7 Ah thanks for the reply. Much appreciated! Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 7 Author Share Posted February 7 (edited) Sorry.. Last question. Would this be correct for the other eq pot? https://www.ebay.co.uk/itm/256128635417?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=zc32U3psQnu&sssrc=4429486&ssuid=vNO_rdY8SEe&var=&widget_ver=artemis&media=COPY Depending on the shaft type I have. The blend and volume pots both work fine - it's just the eq pots that need changing. Also, I have soldered basic pots before - if I'm careful how I solder and heat shrink everything, am I right in thinking this is straightforward and I could do it myself? Edited to change the Ebay link as I posted the same one... Edited February 7 by Jamesemt Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 7 Share Posted February 7 (edited) 7 hours ago, Jamesemt said: ... Would this be correct for the other eq pot? https://www.ebay.co.uk/itm/256128635417?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=zc32U3psQnu&sssrc=4429486&ssuid=vNO_rdY8SEe&var=&widget_ver=artemis&media=COPY Depending on the shaft type I have. The blend and volume pots both work fine - it's just the eq pots that need changing. Also, I have soldered basic pots before - if I'm careful how I solder and heat shrink everything, am I right in thinking this is straightforward and I could do it myself? ... Hmmm - from your latest question it sounds like your controls don't match the schematic above - It shows 3 control pot units: Vol, Bass & Treble (where Treble is a tandem pot, one track for Active and the other for Passive) Could you list how many separate pot position you have on your control plate (and mention any switches/selectors, too) please Which of these you've just listed have a centre detent? Thanks Yes, if you're just replacing potentiometers, and you've soldered before, you should be ok changing these out [Ignore this following para if you've used heatshrink before. Cut each length of heatshrink to be long enough the cover the solder joint and extend over the wire insulation by 1/4-1/2" (use the non-soldered part of the tip to shrink over the solder joint). The heatshrink obviously needs to be on the wire before soldering, and slide it an inch or two away from the joint being soldered, before sliding it back to shrink] Change out 1 pot at a time, noting wire-colour-to-lug-position - use just enough solder to get a slim, stable solder joint that the heatshrink can slide over easily If the control cavity is well-shielded, and connected to ground, you should avoid trying to solder ground connections to the potentiometer cases Edited February 7 by sandy_r 1 Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 7 Author Share Posted February 7 Thanks yes used heat shrink before. So my Jazz plate is: Volume Pickup blend with indent and a pull up for passive (which I never use) Treble with indent Bass with indent Thanks Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 7 Share Posted February 7 (edited) 39 minutes ago, Jamesemt said: Thanks yes used heat shrink before. ... Volume Pickup blend with indent and a pull up for passive (which I never use) Treble with indent Bass with indent ... Ok, so you have a Blend pot in addition to the example schematic shown above - if that pot and the Vol are operating ok - and you're certain that you'll never use Passive setting - then you only need to source 2x 250k linear pots with centre detents (and suitable shafts): 1 for the Bass control, and the other for just the Active half of the Treble control If you can't find single-track pots with centre detents for a reasonable price in the UK (after checking with the sources found via Google, as indicated earlier), then you could still use one track of linear tandem blend pots - 1 half of first tandem pot for Bass, 1 half of 2nd tandem pot for Treble The earlier eB*y link 250k linear pot with centre detent shows that you could get 2x 250k linear tandem pots with centre detent for approx £12, incl P&P, dispatched within a day If you source the pots and want to wire them in yourself, you'll need to sort out the correct track/wire/lug config for the Active Treble - if you're unsure then a friendly BCer will be able to help Good luck, have fun! Edited February 7 by sandy_r Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 7 Author Share Posted February 7 (edited) Thanks Sandy - I've got those ordered. So bass top set of tracks on first pot. Treble second set of tracks on the second pot. If anyone is reading this, can they confirm how to wire in just the active side? Thanks for everyone's help so far!! Just realised I've been referring to detents as indents 😂 You live and learn! Edited February 7 by Jamesemt Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 7 Share Posted February 7 (edited) 2 hours ago, Jamesemt said: ... So bass top set of tracks on first pot. Treble second set of tracks on the second pot. If anyone is reading this, can they confirm how to wire in just the active side? ... To confirm Active track on existing Treble pot: before starting to change in new pots, disconnect the 3 wires from ONE track on the existing Treble pot - with Active switched on, does the Treble pot still work? If Yes, you need to use the 3 wires still connected, otherwise use the 3 wires just disconnected Connect the 3 wires to 1 track of the new pot - but keep heatshrink slid back from joint Test bass with new Treble pot - Max Treble should be fully clockwise turn to the control knob - if not, swap outer 2 lugs of that pot track When Treble operating in correct sense slide heatshrink into place & heat. Cover any exposed wire ends with some heatshrink Edited February 7 by sandy_r Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 7 Author Share Posted February 7 You are a star!! Thanks for this. 1 Quote Link to comment Share on other sites More sharing options...
sandy_r Posted February 7 Share Posted February 7 Hardly, but thanks for kind words! ... don't forget that the Passive Treble will be non-operational (if Active is only track connected - and if you did connect the Passive track, then it would likely operate in the opposite sense to the Active - Max Treble at fully CCW) Good Luck! Quote Link to comment Share on other sites More sharing options...
Jamesemt Posted February 7 Author Share Posted February 7 30 minutes ago, sandy_r said: Hardly, but thanks for kind words! ... don't forget that the Passive Treble will be non-operational (if Active is only track connected - and if you did connect the Passive track, then it would likely operate in the opposite sense to the Active - Max Treble at fully CCW) Good Luck! OK thanks!! Quote Link to comment Share on other sites More sharing options...
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