Dead_Nid

The Oberheim OB-XA, a synth from the 80's, uses the connectors on the photos to connect voice cards to the main board. I want to replace them all and am trying to source them but I don't even know their name. thanks in advance for any help! ps. sorry for the crappy mobile pics, but I think anyone who is familiar with such connectors will figure it out.

greetings Audioguru! Hi Ante! Glad u remember me! Our console's PSUs were finally relieved from their pain with some great BHC filter caps and a neat job refurbishing almost everything. A big fan (a home-use one) cools them down especially on these hot summer days that they need it so much. Thanx a LOT for these links, they are really very helpful! I will come back when my knowledge is stronger and am preparing to build a regulator or a balanced power transformer or both! Meanwhile if anyone has a suggestion, sharing it would be wonderful. Especially for DIY 230V single-phase regulation. thanx again! take care

you're kidding me! Is it such a complicated device this power conditioner thing? No one of you electricity experts ever built or planned to build one from scratch? Apart from being very interested in building one for my needs, I am also so curious to find out why conditioners (AVR whatever they are called) are so expensive even in the low Watt range. Also all these AVR advertised UPSs do anything at all to regulate the mains voltage or is it just a "theoritical" AVR? Sorry if i'm putting up primitive questions and sorry that I don't have the time to investigate this thing all the way by myself. I need some guidance, somewhere to start, please. Comments, links, cheers, swears...something Thank you all and best regards!!! Nick

Hello folks! Anyone ever got involved in a DIY Power Conditioner? Capable to handle at least 1000VA. Please share thoughts and/or schematics. Does anyone know if this cheap APC Line-R 1200VA Power Conditioner is any worth at all? I find it strange to be so low in price (about 50euros here) when professional power conditioner cost a hell lot more. Thanx a lot!

thanx indulis. please explain "inrush current". have you read the rest of the thread? It is a linear regulated psu. thanx again!

Happy new year to everyone! Haven't tried any special diodes yet. I want to ask two very newbie things that I am curious about: 1) My PSU uses two 4700uF smoothing caps (in parallel so total capacitance is 4700x2). I am going to replace them because they are very old. But as the opportunity arises I could replace with greater capacitance. Is that better in smoothing quality (apart from space and cost issues)? Remember, this an audio mixing desk's power supply. So...I am thinking of placing 6800uF or 10000uF and that will mean a total of 13600uF or 20000uF...Even theoritically, is there any benefit as the capacitance gets higher and higher? Is there any chance that it can cause trouble instead? 2) What about voltage ratings? I was told (by Dan Lavry) to use caps with voltage ratings as low as possible. But in some manufacturers charts I have seen that the higher the voltage rating the lower the impedance. Any clue? I am between BHC, Nichicon and perhaps Black Gate caps. Any suggestions? Thank you! Best regards and happy,creative 2006!

Thanx Ante. I haven't done any mods yet...too much damned work...but I am going to start very soon.

hmmm bloki, do you know if the LT1083 or LM338 will oscillate when caps have low ESR? Ante, have you ever used all these diode types in linear regulation circuits so as to make a fair comparison? Best regards, Nid

Hi Ante, you are right. Even though I have currently no known problems I think I am trying to accomplish the most efficient, clean energy (RF free) power supply I can make for my mixing desk. Nevertheless I've read that Hexfreds give a significant performance gain in the overall sound such as better resolution and reproduction of high frequencies and dynamics. Maybe that is another hype, that's why I am trying to get other people's opinions. Thanx a lot! Best regards, Nid.

...by the way, is "Schottky" and "Shotkey" the same thing? What about FRED and Hexfred? Is there any difference in performance between using discrete diodes and bridges?

Hi dear friends! I've recently discovered the existence of Shotkey and Hexfred diodes which are said to be the best type used for rectification in audio PSUs. Can someone enlighten me on this as well as diodes in general? (fast,soft recovery etc) Thanx a lot! Nid

Hi! In the rail were caps get hot I measured 21.7VDC and 0.04VAC from the rectifiers' output whereas in other rails (where caps don't get hot) the AC voltage was max 0.02VAC. These 40millivolts can't be the cause for heat in the caps, can they? Caps are within specs. Old caps were also getting hot in the particular rail. I don't think that there should be a higher current drawn from that rail than from the others (with same outputs) but I am not sure about that. It has same design but different components though. Should I replace the diodes? (current diodes are "standard recovery") Thanx, Nid.

hope someone checks this question out: Is it natural for a polarised aluminum electrolytic capacitor to get hot? What can the reasons for that be? I am not talking about small ones (let's say at least 4700uF @ 16V). Thanx!

thanx Ante. Is this stuff nice for cleaning reel-to-reel tape recorders' heads too? MP, what 0 ? If you mean the 0 at my rough drawing then this is the resistance at pins 2-3 at gang-1 and 1-2 at gang-2 ONLY when the pot is at the fixed center position. If I rotate it then the resistance rises with values from 0 to approx. 88K or 82K (depending on the gang).

Hmmm, if you mean acoustic levels I think about 2db max. My speakers were never out of phase, I mean for several years...hey I am a damned sound engineer. lol...not everyone is an audio guru. OK. Here I have in front of me 2 spray cans. Both Philips. One is the blue "DEGREASER CLEANER", the other is the red "CONTACT CLEANER". So, the blue should be good for cleaning e.g. connectors. The red should be good for cleaning pots. Correct? Yeah actually I am using graphite (in powder or spray can) for hinges too. I only used WD40 in the past. However I didn't know it was that "messy". I'll try to find and buy a "video drum cleaning spray". Is there a particular product I should check out? Now I am really curious...I need to get a WD40 and do some ghost-busting...Isn't there a chance it blows in your hands? ;D ;D ;D

audioguru I had done the following thing which I forgot to mention: I fed some line level inputs (the CD input if it matters) with a constant 1KHz sine tone from a PC pro audio interface. I measured the VAC at both channels right at the input and it was exactly the same amount of a few mVolts. Then I measured VAC at the speaker outputs and found out that there was about 500mV difference with the speaker playing lower getting the fewer volts (so I can't be wrong about my ears). Then measured the outputs of the preamp and there was a respective difference. So I am sure that the unequality comes from the preamp but I am not that good to find out where exaclty without a schematic. But I think that the pots are the first to suspect, right? There are actually four 2-gang pots in the preamp section. They control bass,treble,balance,volume. I took all of them off and measured out of circuit. All show some difference in resistance between gangs but the one for the balance control was the worst. I am going to post schematic soon. Sorry for altering the initial subject of this thread but I think we had enough interesting posts on how to clean a pot (at least a carbon pot). I will personally follow the "contact cleaner without any grease" way. Products like the blue Philips degreaser spray. Definitely not going to use the WD40!!! Though it does a great job when my doors' hinges start to squeak

Hi! I am measuring out of circuit of course. Now I don't think that this pot has a wiper. In the center position there is a clearing on the carbon layer like there is no carbon there. I don't know if that is called a wiper. So here is a rough drawing to help you get the picture of what I am measuring with my multimeter: (that is on center position) PINS->

Hi! This is a 2-gang pot metal-shaft with a center click fixed position made by ALPS. Type 100KMN. It is used for the balance control between the 2 speakers. So when it is in the center position it should measure 100K for gang-1 and 100K for gang-2. However it measures 88K and 82K respectively. As I told before, my left speaker was playing a bit lower than the right one. Is this 6KOhm difference audible or am I searching in the wrong place? MP, 100k sure is pretty standard but it is also a matter of dimensions and it is ALPS, rather good quality...I got a plastic pot from Piher from a local store to replace a volume pot and yikes...Raising the volume you could hear the signal swinging from one speaker to the other. Then I measured it gradually and found out that my ears were right. So, I will definitely replace the pot but not until I find a good one and that's not an easy thing to do in my country. That's why I am looking for international stores to order from. One last thing that just came to my mind. Let's say I don't need the balance control. I want my speakers to play equally everytime. So isn't it reasonable to put two 100K static resistors in place of the pot? (Does it matter if it is a little less or more than 100K?) But the total resistance for each channel should be equal. Common resistors are not that accurate as far as I know. Let's say that you buy 2 resistors of 47K. One might measure 45K and the other 48K...so same shit. Is there some type of resistor that is very accurate? Thanx!!!best regards!

Hi! I guess when the specs of a pot have changed there is nothing more you can do to save it, right? I am trying to refurbish an old 100K stereo pot. At its fixed center position it gives about 10K difference between channels, measured on its own (not on any circuit). After some cleaning I managed to narrow the difference down to 8K...waste of time. So I guess this is why my left speaker plays at a slightly lower level than the right speaker for about a year now...(The pot is for the Balance control). Best regards!

And don't forget to mention the actual procedure that you follow. For example is it better to open the pot and clean directly the internals or just throw some spray from any opening and rotate the shaft a few times? such stuff...cheers!

Hi all! Done a search on the subject in the forum and found almost no info. I thought it would be beneficial for all to gather some opinions and tips on what is the ideal way to clean an old potentiometer. Mostly refering to the ones using carbon but any info on other types is mostly welcome. Personally, I've heard that it is best to use a Contact Cleaner (degreaser) spray with no grease of any kind. If using one with grease then this grease may make matters worse some time later when it dries out. true? false? other?

A million thanx Ante, this is great!!! :-* On to work now. Best regards! Nid.

Greetings audioguru (hey! I want to be an audio guru too when I grow up!

Hi! Do you know of any high grade pots and some store to order them from (in Europe preferably)? I know of ALPS but I can't find any resources to buy. Don't know if that is of any importance but I need stereo pots (both linear and logarithmic) with metal shaft and without button capabilities. Perhaps an idiotic question: Can one make a modification in an amplifier's volume control so that it uses a simple pot instead of a stereo pot? Thanx, best regards, Nid.