[sdiy] Where to find a suitable power regulator insulator bushing for a Prophet 10?

Steve Lenham steve at bendentech.co.uk
Thu Mar 23 10:18:07 CET 2023

I've seen that from time to time on other US-made stuff - it's just an 
alternative to the shoulder washer technique.

TBH, anything made of plastic that fits should be suitable. The voltages 
present are relatively low in insulation terms, so high resistance is 
not a requirement - it just needs to not be a conductor. And the maximum 
heatsink temperature must surely be only 80C or so (hopefully lower, 
though I understand the early Prophets run pretty hot) or the regulators 
would be shutting down, so you're only looking for a material that could 
survive in boiling water without liquifying.

Get a suitably-dimensioned nylon spacer and Bob's your uncle 
(translation for non-UK readers: that'll be fine).


Steve L.

On 22/03/2023 19:52, antti.s.pitkamaki--- via Synth-diy wrote:
> I’m restoring a vintage Prophet 10. When reinstalling the power supply 
> I noticed it is missing one of the power regulator insulators - It’s a 
> cylinder-shaped piece of semi-transparent fairly stiff plastic through 
> which the screw of the regulator goes. The insulator should be in the 
> hole of the heat sink, preventing the regulator’s screw from short 
> circuiting to the heat sink. The insulator measures as follows: OD 
> 6.4mm (0.25in), ID 4.2 (0.165in), length 3.3mm (0.13in).
> Now when googling for this part it seems the modern equivalent is a 
> type of a shoulder washer - these wouldn’t work, it needs to be 
> ”shoulderless”.
> Any tips on what to use as a substitute? Adequate resistance to heat 
> and high electrical resistance are probably the required features of 
> the material. I was thinking of a silicone tube, cut to the correct 
> length and the inside diameter driller to the correct size (I can only 
> find a tube with the correct outer diameter).
> Another idea I’ve got is a cylinder-shaped nylon spacer, some seem to 
> be a close match.
> Then there’s 3D printing, but dunno about the suitability of printable 
> plastics.
> Any suggestions? It’s strange that no modern equivalent seem to be 
> available. Wine Country couldn’t help me.
> Best regards,
> Antti
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