When is a 330k pot not a 330k pot...

[espidog]

I recently decided to give my 2004 4003 the 'vintage tone' treatment, so I purchased the RIC-supplied CTS 330k pot/pullswitch unit.

Before doing so, I had read and been intrigued by this blog page from 2017:

https://crawlsbackward.blogspot.com/201 ... e-cap.html

In it, the blogger describes how he purchased two of the (nominally) 330k pot/switch units, but when he measured their track resistances he found that both were clearly 500k components.

This didn't put me off buying mine - in fact I found it encouraging news, as my preference is for the treble pup to have as much top end bite as possible.

My 330k unit arrived yesterday. I popped my Fluke meter across its track and it measured out at... 457k - i.e. within 10% tolerance for a 500k pot.

So, personally, I am mighty pleased. It does seem odd, though, and can't help but make me wonder whether CTS has been supplying mis-labelled pots to RIC for quite a long time!

If any other forum members are reading this and you have one of these "330k" pots to hand, why not put a DMM across its track and tell us what it shows? It would be interesting to see what spread of results we get.

[espidog]

Me again!

I'm posting again in my own thread to report another, quite unexpected, anomaly.

I've just finished doing the "vintage tone" mod to my bass. Once I'd taken the old tone pot out of circuit, I put my Fluke meter across it just out of curiosity. According to RIC, my 2004 bass should have been supplied with 330k pots in all positions.

The factory-fitted "330k" tone pot out of my bass measures 170k.

As you can imagine, I was astonished - that's almost half the value it should be! Crikey, no wonder I'd been feeling a lack of "bite" from my treble pup. It's definitely back now I've got the new pot in there.

Makes me wonder, though, what the REAL values of the other 3 pots are? Don't fancy having to de-solder them all just to find out, though, so I think I'll let that sleeping dog lie.

[aceonbass]

This is part of the reason I build wiring harnesses ro replace these under spec tone sucking pots. The shoddy soldering, and poorly constructed ROS output jacks are the other.

[espidog]

UPDATE:

Looks like I couldn't let that sleeping dog lie after all.

Took another look inside my bass today. I've established that when it left the factory it had (nominally) 250k pots in all positions, not 330k as I'd thought - i.e. the pots in my bass are all CTS 07341 code.

I've now measured the actual values of all the original pots (I swapped out the treble tone pot, see further back up the thread for details), and the results are:

Neck Volume: 193k (23% below nominal)
Treble Volume: 195k (22% below nominal)

Neck Tone: 175k (30% below nominal)
Treble Tone (removed): 170k (32% below nominal)

...so, low values all round, with the two volume pots barely scraping the edge of their supposed 20% tolerance, and the tone pots nowhere near it.

I'm sorry to have to say this, but it would appear that - in 2004, at any rate - CTS were sending RIC some pretty out-of-spec components, and nobody at the RIC factory was checking them for consistency.

[aceonbass]

Those new pots ARE 330k pots, They're just so far out of spec that they happen to make good 250k pots....

[espidog]

Those new pots ARE 330k pots, They're just so far out of spec that they happen to make good 250k pots....

Or, in the case of my bass, BAD 250k pots - I mean... 170k?? Jeeez!

Seriously though, Dane, I'm curious. I always laboured under the impression that 07341 = 250k and 07343 = 330k, but it's beginning to sound like these stock codes are nothing to do with pot values at all - is that correct?

[aceonbass]

RIC has changed their wiring diagrams, pot specs, and pot part numbers a few times, so you can't tell what was originally intended. 500k tone, and 250k volume pots were standard till some time in the 90's. In fact, by the late 90's, the pots were specing out at around 175k! The same tone sucking pots were used on 4004 basses and 650 guitars as well.

[antonius]

I emailed a UK supplier of part no 07346, the CTS 330k pot with push pull switch, to ask if he could check out the spec of his stock, as I'm looking for a 500k push pull tone pot for my 1975 4001, and don't really want to buy one at 330k or below. He kindly got back to me and said that of his 9 items in stock most measured about 450k, and one at 510k - all within 10% tolerance of 500k and much higher than the nominal 300k. So this is good news for me and I've placed an order for the 510k one. Thanks to Ken for highlighting this apparently commonplace anomaly.