This was also posted under the Acoustat Answerman thread....
New here to diyAudio. I appreciate the wealth of information and knowledgeable experts here. I recently acquired a pair of Acoustat 2MH's. I've been a big Acoustat fan for 40 years since I got my first set of Model 2's in the early 80's. I haven't yet had a chance to dig into the MK-131 interfaces (the speakers are fully functional), but my question concerns Preventive Maintenance. I want to do as few modification as possible. I understand the "C mod" is highly recommended, but I would prefer to keep the speakers as original as possible. So, my question is this: From the schematics I've seen on here, it seems that there is a single electrolytic capacitor present in the interface. Am I correct in assuming that this electrolytic cap is the only component prone to age-related failure, and therefore the only component that I should be concerned about replacing (given my desire to make as few changes as absolutely possible)?
Thanks for you time.
New here to diyAudio. I appreciate the wealth of information and knowledgeable experts here. I recently acquired a pair of Acoustat 2MH's. I've been a big Acoustat fan for 40 years since I got my first set of Model 2's in the early 80's. I haven't yet had a chance to dig into the MK-131 interfaces (the speakers are fully functional), but my question concerns Preventive Maintenance. I want to do as few modification as possible. I understand the "C mod" is highly recommended, but I would prefer to keep the speakers as original as possible. So, my question is this: From the schematics I've seen on here, it seems that there is a single electrolytic capacitor present in the interface. Am I correct in assuming that this electrolytic cap is the only component prone to age-related failure, and therefore the only component that I should be concerned about replacing (given my desire to make as few changes as absolutely possible)?
Thanks for you time.
I would say the electrolytic capacitor is the most likely to suffer from age. Replacing it can't hurt. If I remember correctly, there are actually two 'lytics - one in the high pass for the ESL transformer, and one for the woofer's low pass crossover. That may be located in the woofer box. Note the C-Mod was a factory-authorized change, and many speakers were modified at a later time. One nice thing about the C-Mod is that the value of the capacitor is smaller, making it a good candidate for replacement with an equivalent film capacitor.
Next up of concern is the 5 capacitors and 5 diodes in the high voltage bias multiplier. These can fail after some time, resulting in reduced efficiency/volume of the ESL portion. A list of replacement parts appears elsewhere in the main AcoustatAnswerMan is Here thread.
Next up of concern is the 5 capacitors and 5 diodes in the high voltage bias multiplier. These can fail after some time, resulting in reduced efficiency/volume of the ESL portion. A list of replacement parts appears elsewhere in the main AcoustatAnswerMan is Here thread.
Thanks for the response. I had read elsewhere about the electrolytic capacitor in the crossover; it hadn't occurred to me to include that along with the one in the "primary" circuit. As I said before, I haven't been able to actually dig through the interface: I'm in New Jersey and the speakers are in Florida. That will be remedied this summer. So, it's quite possible the C-mod was already done to these, although the previous owner said these speakers were unmodified. I understand the potential sonic benefits of going with a film capacitor over an electrolytic. However, as I read over the C-mod instructions, it gets more deeply involved in changes (e.g., replacing transformers) than I care to undertake. Not for lack of ability, but rather lack of desire.
The mention of the diodes and capacitors in the bias multiplier is interesting. It was my understanding that diodes failing due to age, while possible, was very unusual, and that ceramic capacitors effectively don't fail with age. However, I suppose it's a situation of if I'm already in there to replace a couple of electrolytic capacitors, why not go ahead and do the diodes and ceramics. Kind of like replacing belts and thermostats when you need to change a water pump...
The mention of the diodes and capacitors in the bias multiplier is interesting. It was my understanding that diodes failing due to age, while possible, was very unusual, and that ceramic capacitors effectively don't fail with age. However, I suppose it's a situation of if I'm already in there to replace a couple of electrolytic capacitors, why not go ahead and do the diodes and ceramics. Kind of like replacing belts and thermostats when you need to change a water pump...
The C-Mod does not involve any change to transformers. You might be thinking of the Medallion Transformer upgrade, which is virtually impossible nowadays due to a lack of transformers. The C-Mod involves only a change to the resistor-capacitor network feeding the audio transformer in your MK131.
I always considered the diodes and caps in the bias supply to be "forever" items, but in the last few years I've seen reports of failing parts in the earlier models. Nothing last forever.
I always considered the diodes and caps in the bias supply to be "forever" items, but in the last few years I've seen reports of failing parts in the earlier models. Nothing last forever.