Sockets in a PCB to test out various Capacitors and Inductors? (Pultec clone)

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Joined
Jun 14, 2019
Messages
6
I have a couple pultec clones in 500 series format and I want to swap out a handful of inductors and caps in the filter section. I was wondering if I could socket those holes in the PCB with a female socket and then start doing a solderless swap of caps and inductors until I get the EQ shelf and boosts right to my ears on some test recordings.

Has anyone done this?
Can you recommend sockets that will take some different width legs/wires from various components?

Will probably try some newer ones as well as some old russian PIOs and maybe some mustards.

Suggestions and guidance would be hugely appreciated, thank you!
 
Without endorsing the effort, they make ZIF (zero insertion force) test  sockets for IC that are designed for thousands of cycles. Regular IC sockets are not. ZIF sockets are not cheap and usually formatted for dual inline ICs . at least the ones I have seen/used.
A441D200624TL6K4.jpg


For your purposes I will assume you need low impedance connections. Kind of old school but back in the day we used Fahnstock clips for breadboards.
71g2CWiefbL._AC_UL640_QL65_.jpg


JR
 
Thank you! I'm going to include a photo because space is super tight insode this 500 series module, and I have a panel that needs to be installed above these as well.

I would be swapping C15 through C23, that left row.

Would regular low profile IC sockets like these work?

https://www.digikey.com/en/product-highlight/m/millmax/super-low-profile-sockets
 

Attachments

  • 20200806_115449.jpg
    20200806_115449.jpg
    162.4 KB · Views: 32
JohnRoberts said:
Without endorsing the effort, they make ZIF (zero insertion force) test  sockets for IC that are designed for thousands of cycles. Regular IC sockets are not. ZIF sockets are not cheap and usually formatted for dual inline ICs . at least the ones I have seen/used.

Unless he is doing a production run, there is no need for such high contact rating of a ZIF socket, If he is only swapping a handful, like he mentions in his post, to test the sound, I dont think there should be a problem with a regular IC socket.
 
user 37518 said:
Unless he is doing a production run, there is no need for such high contact rating of a ZIF socket, If he is only swapping a handful, like he mentions in his post, to test the sound, I dont think there should be a problem with a regular IC socket.
I have learned the hard way that common IC sockets are not very robust. The OP specifically mentions different width legs/wires. Forcing thicker leads into sockets may affect contact quality for later insertions.

ZIF is expensive, Fahnstock cheaper but perhaps still awkward.

For a small quantity of components you could attach short wire leads to the PCB and tack solder components to those wire leads insuring a good electrical contact. Alternately you could solder alligator clips to the wire leads.
iu

A poor electrical contact in a loose socket connection might introduce an undesirable variable.

Good luck

JR 
 
MillMax make sockets exactly for what you're doing. Here's an example:

mmsock.png


I don't know what these exact receptacles are off hand (might be 0777). Use their "Product Finder" (if you can stand it - it's horrible) to look for "Recepticle with No Tail" and pin diameter ~-.015" - 0.03" or so. Examples are parts starting with:

9354, 8637, 0569, 0777, 6577, 7545

However, if the PCB is not designed for the socket (and in your case clearly they are not), you'll need to drill out the vias which will disconnect top/bottom traces. To fix that, you'll need to carefully scrape away adjacent mask over any connecting traces and then carefully solder-bridge those traces to the socket body directly without ruining the socket hole with solder.
 
+1 on alligator clips on short leads.

if you're into experimenting with non-trivial stuff, expect non-trivial leads and terminals. does not compute to try a one-size-fits-all socketing, even if allowing for small variations in lead diameter

..make that +2 for alligator clips

/Jakob E.
 
+ Another for alligator clips and breadboards, I've done it both ways and it's so much less hassle to just re-clip a couple of leads than powering down and footling around inside the module, reinserting, powering back up etc. Not to mention the radically different lead diameter across different eras and types of capacitor, as others have noted.

Listening tests are fun, and educational if done in a controlled way to minimise bias. I've done similar with filter caps in a variety of EQ circuits including Pultec-style (as I'm sure many here have). When considering what types to test, don't overlook styroflex if you can find the right values from a trustworthy source. To my ears it's a nice-sounding dielectric, but they also come in very tight tolerance which can make matching for stereo use a good deal easier.
 
Female ‘pin header ‘ type work well for this mini breadboarding whip.
I don’t know if molex kk headers comes in female pcb pins but some bits of solid wire could make it so
 
shabtek said:
Female ‘pin header ‘ type work well for this mini breadboarding whip.
I don’t know if molex kk headers comes in female pcb pins but some bits of solid wire could make it so

In the link I shared above there are pictures of this in action. I used female D-sub pins and they are still working several years later.
 
On another note, have you thought about substitution boxes? Lead length might be a problem depending on the circuit (filters might be problematic, particularly for inductor sub boxes. But perhaps a cap sub box at least could make life a bit easier). But you could try it with the shortest possible leads. Either way, this is exactly what they were invented for.
 
rackmonkey said:
On another note, have you thought about substitution boxes? Lead length might be a problem depending on the circuit (filters might be problematic, particularly for inductor sub boxes. But perhaps a cap sub box at least could make life a bit easier). But you could try it with the shortest possible leads. Either way, this is exactly what they were invented for.
We used to call then diddle (twiddle?) boxes and used them for trial and error design attempts. I have a capacitor box and resistor box with a range switch. I don't think I've used either this century.

If you buy an old used resistor box be sure to check the low value resistors, they have a tendency to get burned out by inappropriate use.

I never found these of much use for serious audio design because of the long wire leads, and less than premium components.

Have fun...

JR
 
JohnRoberts said:
I never found these of much use for serious audio design because of the long wire leads, and less than premium components

Yes, agree that most of them have pretty cheesy components in my experience. But I have found the Gen Rad Resistance decade boxes I keep around to be useful as they have 1% Dale RN60 mil-spec metal film resistors (1/2 watt). I also kept an old Cornell Dubilier capacitance sub box, which has 160V CD polystyrene caps in it. I use both of them fairly regularly.

I cut one end off of two pairs of banana plugs and attached Keystone (or maybe it was Mill-Max) pins that fit into the average size PCB hole pretty well. I use those for PCBs and banana-to-grabber type cables for p-to-p.

The Gen Rad resistor decades are especially useful for transformer tests. One box in series with the function generator and one in parallel with the transformer secondary makes it easy to test with different loads and source impedances. Combined with the CD capacitance box also simplifies trial and error Zobel network investigation.

So there are good ones out there. And I would never go back to manually swapping resistors for transformer tests.
 
rackmonkey said:
Yes, agree that most of them have pretty cheesy components in my experience. But I have found the Gen Rad Resistance decade boxes I keep around to be useful as they have 1% Dale RN60 mil-spec metal film resistors (1/2 watt). I also kept an old Cornell Dubilier capacitance sub box, which has 160V CD polystyrene caps in it. I use both of them fairly regularly.

I cut one end off of two pairs of banana plugs and attached Keystone (or maybe it was Mill-Max) pins that fit into the average size PCB hole pretty well. I use those for PCBs and banana-to-grabber type cables for p-to-p.

The Gen Rad resistor decades are especially useful for transformer tests. One box in series with the function generator and one in parallel with the transformer secondary makes it easy to test with different loads and source impedances. Combined with the CD capacitance box also simplifies trial and error Zobel network investigation.

So there are good ones out there. And I would never go back to manually swapping resistors for transformer tests.

The Elenco resistor substitution box is also really good and very low price, it has 1% 1W resistors.
 
The whole Inductor core swap idea usually boils down to Ferrite VS Iron Powder, what I would love is to also have an air core option, too bad that it is only restricted to low values, unless one is willing to add big ass air core inductors in a box, that box might not be the most portable thats for sure, but it surely would be a good DIY idea.
 

Latest posts

Back
Top