| Author | Message | ||
     Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
Hello, I need help, today I was checking the volume potentiometer channel two (this have 2 potentiometer of 10K at once), and the firs one appears to be ok, I reed 11.2K max and min, .56 ohm, but the second one (the first its in contact with the front panel) an I reed 0.9…. k ohm, the max 2….K ohm, the min 5 ohm, I think the second its bad, what do you think? Its bad?, if I need to replaced, can anybody give me the number, or the model of this potentiometer?, my amp its 210HD-130-12AX7 | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
hello?????!!!!?????  | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
anybody here     | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Sorry, been out of commision for a week. I'm not really understanding which pot that you need. You say two pots but both are volume? Are you talking about the volume pot on channel one? Are you talking about the next pot on te chassis, which would be the treble pot? You say the first is in contact with the front panel but they ALL are in the front panel. Please clarify WHICH pot that you need. Mike. | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
Sorry,  ,  ,  , I need the volume pot for the channel two, in the manual appears 10K, this is a dual pot, i was testing all pots and all values are different from the manual, this means that i need change my pot, right? Roberto | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
BTW, the volume pot in the channel two, its a dual pot | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Are you checking the pot IN the circuit or out? If you are checking it in the circuit, it can give you false readings. If you took it out or removed the leadss from it, then yes, it's bad. I'll have to look to see if I can find a part number unless Ed knows it off the top of his head, IF it's available. | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
i checking in the circuit, I'll check out, and write the results, Thanks again Mike, you're a great MM amp resource, thank you for your patience and your help, | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
I did just glance at the schem and they ARE supposed to be both 10K pots so if one only gets to 2k, it's bad. THat second pot is part of the reverb gain structure. The problem will be finding a dual taper pot in 10k | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Haven't been able to FIND a twin taper pot that uses different tapers for each pot. HMMMMMMM? I'll look some more from home. Found a dual pot at digikey but it had twin log(audio) taper, not a log and lin. I'll look some more | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Just went to all the places that I buy from(mouser, MCM, digikey) and NOBODY carries a dual ganged pot with different tapers so it must have been a special buid for the audio guys at MM. THey make a dual pot in 10k but the different taper on the rever gain MIGHT screw up the sound of the reverb. Maybe, if you DO need one, somebody here will hav ean old chassis with the pot good. Sorry. | ||
| Ed Goforth (ed_goforth) Username: ed_goforth Registered: 06-2006 |
What model is this in? One of the ganged pots has a different taper? I need to see a schematic. I have been able to take a dual pot and modify the resistance by placing a limiting resistor across the outside lugs of the pot that needs a different value, say for example, you have a dual 100k AUDIO taper and you need 10k audio and 10k linear. Put a 10k resistor across the 2 outside lugs (terminals) to limit the pots resistance of the particular pot to 10k, and the same for the other at any value needed, but to make the taper different, you need to find the right resistor to put across the top lug (furthest from ground) and the middle (wiper), this will change the taper, I beleive form audio to linear and a resistor across wiper (center) to bottom lug (ground) to simulate audio taper, its one or the other, I have not done it in a while, but have in the past with good results. I hope this helps, it can at least get you into a usable circuit. | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
thank you Ed, my amp its 210HD130-12AX7, my chassis 2275-130, the schematic its in this great site | ||
| Ed Goforth (ed_goforth) Username: ed_goforth Registered: 06-2006 |
Hi, I would try some good quality contact cleaner and spray the contacts and work the pot a bit and see if it clears up first and if that does not work get maybe both a dual linear and dual audio pot, try both in circuit to see if there is much difference. I would go with a audio if you can only get one type, be it 10k or more. If its higher than 10k, say 50k audio, put a 10k resistor across the 2 outside lugs as I described before, and on the linear side (via schematic), try different value resistors maybe 4.7k to 100k across the center lug and 1k resistor (going to ground) side lugs. The resistor across the center and outside lugs makes the taper of the resistance come up quicker, where audio taper is slow in the first part of the turn of the pot. this is the only easy fix that I can think of unless you get both dual pots in both linear and audio and take one of the opposite resistor tracks and put it in with the other pot, now that sounds confusing but it would work if you can get them apart... I hope this makes some sense...  Good luck! Ed | ||
| Josue Roberto Lopez Lobo (jorololo) Username: jorololo Registered: 01-2008 |
thank you Ed, I'll try  | ||
| Ed Goforth (ed_goforth) Username: ed_goforth Registered: 06-2006 |
This 10k lin pot side of the gain circuit that works with the reverb is very simlar to the Hermida Zen Drive overdrive pedals "VOICE" control, accept that instead of going to ground (as here in the Musicman), it goes to a B+ source on the Zen Drive You could put a trim pot wired as a variable resistor across the middle and ground side of this pot to dial in a close resistance taper and then measure the resistance across that trim pot if you just want a fixed resistor. I'm just throwing ideas at you | ||
| Thomas Leong (tyguitar) Username: tyguitar Registered: 03-2009 |
Audio or LIN pots will both do fine. To preserve the original pot taper value...say it is 2 K now but should be 10K, carefully open the pot and scrap the outer and inside edge of the taper track and check with ohms meter. Scraping some carbon from the track will soon restore it back to 10K. Only takes a short while and patience to do it, measure at intervals while you at it. The pot will be as good as new. |