What are these potentiometers? I need replacements - Page 1
Forum section: electronics / beginners

author: py-bb
author_rank: Regular Contributor
timestamp: April 09, 2023, 09:54:51 am
content: The thing with the "+"-shaped hole (NOT the post that's a capacitor) in it for adjustment is a potentiometer, it's like a metal cylinder with a cap and a normal cheap pot "on top" - I don't think it has any special properties.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 09, 2023, 11:06:39 am
content: They are called "trimmer" pots. Have you searched for that term?

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: April 09, 2023, 11:08:55 am
content: They are just trim pots in a can, they were quite common.The can is not necessary.Look for trim pots on e bay and find something of the correct ohms and wattage that will fit into the existing holes

author: py-bb
author_rank: Regular Contributor
timestamp: April 09, 2023, 11:31:03 am
content: Quote from: jpanhalt on April 09, 2023, 11:06:39 amThe word "potentiometer" is in the title you can assume I've put that into ebay.I wanted tocheck they're archaic but otherwise not specialbefore putting those little crappy ones with the 3 pins and the slotted bit you turn

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: April 09, 2023, 11:48:36 am
content: Most of the time they use "Trim Pots" rather than potentiometer for these types of potentiometers.I included an e bay posting of your trim pots:Yours are probably wire wound and a bit better than most but anything that will handle the power involved would be OK.I do not know how much power is on that board. I do not think it is very much though.I agree that the little blue ones can be "crappy" I use them all the time. Some of them are not made very well. However many pieces of test equipment have used them (including HP) but I think the quality of the apparently identical blue pots is better in more expensive equipment. If the blue pots are "Bournes" brand they are usually much better. (or any other trusted brand.)It would be nice to have a component that would "fit" into the holes on the board. Make installation and adjusting much easier.https://www.ebay.com/itm/183183778489?hash=item2aa69aa2b9:g:HTwAAOSwvHRa1l1e&amdata=enc%3AAQAHAAAA4JFs%2FWMTsYURPyawiO2W99N1ccw0q9z2FVlizx2gztmSpDd1S9wI2LZYpDMFp2Dke9YHpoqChI5udlDwobYez%2FX830yT9LpUb9Cj%2FHPl%2B80HxHU3HAN3YIyJf87NHh9oPCDNT8sqzEM4L%2FbrksKjTgdyjwyhxbhzMl0f%2B9udCFG%2FChENg3uxJc2pVYR86OSsH%2F%2F4wsC7JzvVftZED%2FFhlGM33jc0gns1FDYGYrU%2FSpHiVRYLz1oFJejbg9ZjYTizfV65N4a%2FvVGL0IURY6gksVhLnF18a4znZlkVSvFZF05k%7Ctkp%3ABk9SR77RvtzsYQ

author: jpanhalt
author_rank: Super Contributor
timestamp: April 09, 2023, 12:21:33 pm
content: Quote from: py-bb on April 09, 2023, 11:31:03 amTrim is short for "trimmer." It was not clear whether you searched specifically for trim pots. They are usually designed for PCB mounting and rated rotational life is less. Good luck.

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2023, 03:42:06 pm
content: Quote from: py-bb on April 09, 2023, 11:31:03 amIn English-language electronics terminology, if you say “potentiometer” or “pot”withoutsaying “trim”, it’s assumed that you want a potentiometer intended for user interaction. The ones on PCBs for fine-tuning a circuit, not intended for user interaction, are basically always called “trimpots”, “trimmers”, “trimmer pots” or the like.So if you just search for “potentiometer” without the key word “trimmer” or similar, you’re not going to find what you need.

author: Testtech
author_rank: Regular Contributor
timestamp: April 09, 2023, 04:34:19 pm
content: These are higher power wirewound pots. I clean them with a little Dexoit 100% and they usually work fine, unless they have been overheated.

author: py-bb
author_rank: Regular Contributor
timestamp: April 09, 2023, 04:50:03 pm
content: Quote from: Testtech on April 09, 2023, 04:34:19 pmWhat makes you say that? As far as I can tell when you turn them the metal tab that is connected to the pivot with the "+"-shaped-hole in it turns with it. It's quite a big tab which I thought odd for a pot.I might take one off and look underneath. The one pictured looks like it might have something underneath but others don't. I'll get back to you with pictures as I thought the design crappy.

author: py-bb
author_rank: Regular Contributor
timestamp: April 09, 2023, 04:51:05 pm
content: Quote from: tooki on April 09, 2023, 03:42:06 pmMate I've told you several times on several threads to stop this, I started politely then veered into "stop being an overly pedantic twat" to hints to sod off:https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313&_nkw=potentiometer&_sacat=03rd result.Even if the were actually called "Tookiometers" it wouldn't be relevant still as potentiometers finds them. This isagainlike ethernet cable/RJ45/8C8P/whatever situation - even if one of the names is right it doesn't matter and you'rereally annoying- you've got no excuse to be oblivious to it still.Sod off please.

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2023, 05:01:53 pm
content: Quote from: py-bb on April 09, 2023, 04:51:05 pmStop what, helping you? In this thread, I gave you advice on how to solve your problem by finding the part you need, since you failed on your own. It’s completely practical advice as confirmed by several other people telling you the exact same thing.P.S. You didn’t start off politely in the other thread, you were rude to me from the start.Edit: Looking at your posting history, I suspect you’re confusing me with someone else with whom you have had longer altercations. You and I have had very few interactions (including this one, I’ve responded to you only 3 timesever), and in only ONE (the fuse thread) did you ask me to back off, though clearly even there you already thought we’d interacted before when we hadn’t. (Before the fuse thread, we’d only had a single exchange where you gave objectively bad advice and I objected to it brieflybecause it was safety-related, you responded with a long tirade of more nonsense and a snippy “don’t overthink it”, to which toldyouto be quiet. That’s it.) Hint: I’m not the only forum user with a fairly short username that starts with “t”.Regardless, in the short time you’ve been here you’ve managed to rub a lot of people the wrong way with your abrasive, condescending attitude even when you provide bad advice, and ask questions that indicate your own lack of research and communication skills, then get mad at people who correct you or even just tell you how to solve your problem. I recognize that I, too, can be abrasive at times, even when I don’t intend to, but you’d also do well to try and be a bit more chilled.

author: alm
author_rank: Super Contributor
timestamp: April 09, 2023, 05:23:22 pm
content: Quote from: py-bb on April 09, 2023, 04:51:05 pmPlease stop acting like an asshole and stop biting the hands that feed you useful information. Terminology of how components are commonly called is important information when you're looking for a part. For example see howMousermakes a distinction between potentiometers and trimmer resistors. Just because that some sellers will list as many keywords as possible does not mean all sellers will.

author: Fraser
author_rank: Super Contributor
timestamp: April 09, 2023, 05:48:13 pm
content: Tooki,You have my sympathy ! No good deed goes unpunished !You did your best to help with some very relevant information. Suggest you put this py-bb person on your ignore list as I have just done !

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 09, 2023, 08:24:22 pm
content: I don't think those are wirewound, they just have a carbon arc and a wiper just like most trimmer pots. However, that style is quite old and I don't find them any where. I saw them before. Perhaps different style of same value should work. I don't worry about wattage as those don't have high power rating than normal trim pots. But of course those pots can be removed and tested to make sure that they are bad. They may have value stamped on them too.

author: mariush
author_rank: Super Contributor
timestamp: April 09, 2023, 08:43:24 pm
content: Due to the larger diameter, it may be the case those trimmers can be much more finely adjusted (compared to current trimmers) but still be just "1 turn"If that's the case, you may be needed to resort to trimmers with 4-10 turns .. like for example something like this :https://www.digikey.com/en/products/detail/bourns-inc/3339P-1-103LF/1088290

author: Jwillis
author_rank: Super Contributor
timestamp: April 09, 2023, 08:54:28 pm
content: Quote from: py-bb on April 09, 2023, 09:54:51 amOn Ebay try searching Vintage Trim Pot. Not sure if these will be close or not.https://www.ebay.ca/itm/153511411407?hash=item23bdfe3ecf:g:o9UAAOSwfUZc9DkBYou could try other sources for vintage parts outside Ebay. Not sure what you may have available to you.good luck

author: TimFox
author_rank: Super Contributor
timestamp: April 09, 2023, 09:33:39 pm
content: I have seen quite a few of that style of trimpot in -hp- equipment (this photo is obviously of an -hp- unit).They were generally wirewound--probably for good temperature co-efficient.Being open to the elements, they could sometimes develop bad surfaces, which could be reversed by a few back-and-forth rotations before setting.In a Fluke 845 manual, a similar part is listed as "RES, VAR, WW, 2k, 5%, 1.25 W, PWB MTG".Its manufacturer's code is 71450 (which I can't find quickly), p/n 1110-202-1.25W-5%

author: Swainster
author_rank: Frequent Contributor
timestamp: April 12, 2023, 08:42:15 am
content: I've just been twiddling something similar these in a Keithley - I guess they were a common style of trimmer at the time. Keithley calls these particular ones out as 1NS-115, a 2W 20% variable, wirewound. However, this may be a manufacturer specific version as I've only seen this designation on Keithley parts lists. They look slightly larger than the ones in the OPs pic.Actually these ones look rather like the OPs:https://www.ebay.com/itm/173779660667,and there is a nice photo of the wire element inside.For manufacturer codes i generally use the google search term "cage code xxxxxxx", which for 71450 comes up as CTS,https://www.ctscorp.com/company/history/.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: April 13, 2023, 11:57:34 am
content: I have also seen this type of trim pot used on old radios where the big pot is used to adjust larger signals or higher power.Some of these radios are near 80 yrs old and the trim pots are still OK, if you clean them.One example is the BIAS on electron tube grids.In these cases the part needs to handle higher poser than most little trimmers.If a spray cleaner does not work then...I have removed them and cleaned them using a mild acid, vinegar and a little brush. Then using isopropyl alcohol.You can see the wire wound element when you remove the pot.The resistive wire can get corroded as it is not coated with anything.The board you showed looks like part power supply and part amplifier, where the current through the pot may be a bit high for little trim pots.EDIT: If they do not get too hot a little wax on the resistive coil makes them work much more smoothly.