I purchased an Audible Illusions Modulus 2D about 4 years ago as part of my exploration into the world of tubes. I had a rough start, as it showed up at my door with a damaged face plate and it sounded horrible. I packed it up and sent it down to Art Ferris of AI in Florida. It took some time to get it back, but it eventually showed up with a replacement face plate, a good set of tubes and a clean bill of health having been checked over and a few other things replaced and adjusted.
I loved what it did for my system. I had also gotten back into vinyl and picked up a very nice Counterpoint amp. Everything just seemed to be working great together.
Things got tight soon after that with my employer closing down and etc. I found myself having to cut back and ended up using the system not just for my own audio pleasure but also family HT use as well.
The system was located in a wall cabinet to discourage little hands from exploring knobs and buttons. Normally, I just opened up the door of the cabinet about a third of the way during use. I had monitored the temperature of the preamp and amp a few times like this by feeling the cases and they seemed OK.
Unfortunately things didn't always go as they should, and on a few occasions while I was playing music I wondered out of the room. When I came back later I found the door to the cabinet closed and the amp and preamp hot to the touch.
Eventually my Counterpoint amp failed, although for completely unrelated reasons having to do with wiring. I have missed my system since then, and want to get something working again with the AI preamp and some Quicksilver amps I picked up.
I was pretty sure it was time for new tubes in the preamp after all the use it had seen. It had started sounding flat to me. I wanted to check again to see what tubes had been installed. When I removed the preamp cover I discovered discoloration on the PCB around the diodes by the power supply which looked like heat damage. The anodizing on the preamp's cover directly over the transformer had been affected as well. I had remembered seeing the anodizing faded in that area from the outside previously, but did not recall noticing the discoloration on the PCB before.
I realize this preamp is probably 20 years old, and there may be other issues with it of greater concern like the need to replace capacitors or who knows what else. But it was checked out thoroughly 4 years ago and did work very well for me up until the spring of this past year when my amp failed.
For those that have had experience with these Modulus preamps, and other tube preampss, should I be concerned with the condition of the PCB and/or the diodes located in the area by the transformer where the discoloration is?
I am wondering if this is something that is to be expected after 20 years of use or if it is my fault because I allowed it to get too hot on a handful of occasions when the cabinet door was shut accidentally or if this is something that is inherent to the design of the Modulus preamp and it running hot as I know there are later versions that use a separate power supply.
Sorry for the novel. Lousy pics below. Appreciate any feedback.
I loved what it did for my system. I had also gotten back into vinyl and picked up a very nice Counterpoint amp. Everything just seemed to be working great together.
Things got tight soon after that with my employer closing down and etc. I found myself having to cut back and ended up using the system not just for my own audio pleasure but also family HT use as well.
The system was located in a wall cabinet to discourage little hands from exploring knobs and buttons. Normally, I just opened up the door of the cabinet about a third of the way during use. I had monitored the temperature of the preamp and amp a few times like this by feeling the cases and they seemed OK.
Unfortunately things didn't always go as they should, and on a few occasions while I was playing music I wondered out of the room. When I came back later I found the door to the cabinet closed and the amp and preamp hot to the touch.
Eventually my Counterpoint amp failed, although for completely unrelated reasons having to do with wiring. I have missed my system since then, and want to get something working again with the AI preamp and some Quicksilver amps I picked up.
I was pretty sure it was time for new tubes in the preamp after all the use it had seen. It had started sounding flat to me. I wanted to check again to see what tubes had been installed. When I removed the preamp cover I discovered discoloration on the PCB around the diodes by the power supply which looked like heat damage. The anodizing on the preamp's cover directly over the transformer had been affected as well. I had remembered seeing the anodizing faded in that area from the outside previously, but did not recall noticing the discoloration on the PCB before.
I realize this preamp is probably 20 years old, and there may be other issues with it of greater concern like the need to replace capacitors or who knows what else. But it was checked out thoroughly 4 years ago and did work very well for me up until the spring of this past year when my amp failed.
For those that have had experience with these Modulus preamps, and other tube preampss, should I be concerned with the condition of the PCB and/or the diodes located in the area by the transformer where the discoloration is?
I am wondering if this is something that is to be expected after 20 years of use or if it is my fault because I allowed it to get too hot on a handful of occasions when the cabinet door was shut accidentally or if this is something that is inherent to the design of the Modulus preamp and it running hot as I know there are later versions that use a separate power supply.
Sorry for the novel. Lousy pics below. Appreciate any feedback.
Those blue things with the pinched ends are probably the cause of your overheated diodes and transformer. They are insulated by a water solution, which vaporizes out past rubber seals in 20 years, and they start leaking electrically. There are certain long life electrolytic caps that might last 40 years, but not the rubber sealed ones. I replace all electrolytic caps about 15-20 years. Others here suggest you test them first. The tester is only about $150 calibrated, or $90 kit. I just replace them based on the calender.On a power amp you can measure the output power at the speaker going down as they age, but on a preamp all you can see is possibly the ripple current. You can buy long life 4000-10000 hour caps now, check the life rating at the distributor selector table or the manufacturer's datasheet. These might last more than 20 years.
Read the high voltage for newbies thread at the top of the tube forum, so you don't kill yourself electrically. Use a pair of safety glasses to desolder, solder splashes. I use scrap wire dipped in Oatey #5 solder paste to remove old solder, but wash with a paper towel afterwards, it makes an acid. Mark the PCB with the plus first, if you get a new one in backwards they boil out immediately. New ones are radial lead, the axial ones like shown here are almost all short life garbage now. I tend to cut the leads off the old cap anyway and hook the new leads over after bending. That way you don't damage the PC board and don't even have to unmount it.
You might also have damaged diodes after the caps started leaking. when you have the caps out, check your diodes that they read about 600 ohms forward and 1999 ohms backwards. If they are below 450 ohms either way, replace them with 1n4007 or something. This corresponds to a forwards voltage of about 600 mv and backwards of whatever, up to 1000 v for the 1n4007. Forwards is with the meter black on the line end of the diode.
On another topic, some power amps are not sensitive to the wiring as others have been. Ones based on the LM3886 IC have a built in short sensor. At the low end there are several chip amp kits sold by vendors, I am familiar with the djoffe one. At the upper end, pro PA amps like the Peavey CS800s have built in short circuit speaker wire detection with current transformers and a microprocessor.
Read the high voltage for newbies thread at the top of the tube forum, so you don't kill yourself electrically. Use a pair of safety glasses to desolder, solder splashes. I use scrap wire dipped in Oatey #5 solder paste to remove old solder, but wash with a paper towel afterwards, it makes an acid. Mark the PCB with the plus first, if you get a new one in backwards they boil out immediately. New ones are radial lead, the axial ones like shown here are almost all short life garbage now. I tend to cut the leads off the old cap anyway and hook the new leads over after bending. That way you don't damage the PC board and don't even have to unmount it.
You might also have damaged diodes after the caps started leaking. when you have the caps out, check your diodes that they read about 600 ohms forward and 1999 ohms backwards. If they are below 450 ohms either way, replace them with 1n4007 or something. This corresponds to a forwards voltage of about 600 mv and backwards of whatever, up to 1000 v for the 1n4007. Forwards is with the meter black on the line end of the diode.
On another topic, some power amps are not sensitive to the wiring as others have been. Ones based on the LM3886 IC have a built in short sensor. At the low end there are several chip amp kits sold by vendors, I am familiar with the djoffe one. At the upper end, pro PA amps like the Peavey CS800s have built in short circuit speaker wire detection with current transformers and a microprocessor.
Last edited:
Thanks for the feedback Indiana.
I will probably order the caps and diodes for the AI when I place my order with Digikey for the stuff I need to rebuild the output stage on the Counterpoint. I was lucky enough to come up with some used Mosfets pulled from a SA20 that had one working channel and was being cannibalized. I'll need new gate resistors, protection diodes, insulating pads and thermal heatsink compound. Plus I still don't have a variac of my own...wish I had a local club to turn to. Oh well...its an investment.
I have been sort of scowling down into the case of the Modulus at all the "Wondercaps"...ugh...and basically "Wondering" if they should all be replaced as well...not a cheap proposition I'm sure. I really just want the thing safe healthy and working again...any thought on how I should proceed?
I will probably order the caps and diodes for the AI when I place my order with Digikey for the stuff I need to rebuild the output stage on the Counterpoint. I was lucky enough to come up with some used Mosfets pulled from a SA20 that had one working channel and was being cannibalized. I'll need new gate resistors, protection diodes, insulating pads and thermal heatsink compound. Plus I still don't have a variac of my own...wish I had a local club to turn to. Oh well...its an investment.
I have been sort of scowling down into the case of the Modulus at all the "Wondercaps"...ugh...and basically "Wondering" if they should all be replaced as well...not a cheap proposition I'm sure. I really just want the thing safe healthy and working again...any thought on how I should proceed?
Be careful, the AI is an advanced design, beyond what you might think as 'appropriate'. If it uses 'Wondercaps' it is because they sound better in that location, nothing more, nothing less.
Just talked to Art Ferris. The 'damage' to the board is NORMAL, due to mounting the diodes too close to the circuit board. It would be best to upgrade to high speed diodes, and space them slightly off the board. Not to worry, however.
Just talked to Art Ferris. The 'damage' to the board is NORMAL, due to mounting the diodes too close to the circuit board. It would be best to upgrade to high speed diodes, and space them slightly off the board. Not to worry, however.
Last edited:
Film dielectric caps are good for 50 years at least, since they became reliable about 1966 from Sprague Mallory & Goodall. These do not have a pinched end, do not have a plus on one end, and tend to be in sizes 2 uf and under, although there are some huge ones 10 uf to 50 uf. The ring on one end is not a minus, that is the outer wrap. Don't know if a "wondercap" is a film cap, but I suspect so. At least from the pairing of the word "wondercap" and "don't worry".
"high speed diodes" are called "fast recovery diodes" by newark and mouser. Make sure the PIV exceeds the rating on your electrolytic caps- probably 450 V or more for tube B+.
Thaumatarge agreed with me on "chat" about causes of problems- in old gear, electrolytic caps are problems waiting to happen. 5 years for the cheapest of consumer gear, 20 for the average life cap, longer for special epoxy sealed e-caps but you have to have an old catalog with the part number in it to find out if you have any of those. Not very likely in gear sold to consumers. None of my $5000 new organs had any long life E-caps. That was more money than a tricked out muscle car in 1968.
"high speed diodes" are called "fast recovery diodes" by newark and mouser. Make sure the PIV exceeds the rating on your electrolytic caps- probably 450 V or more for tube B+.
Thaumatarge agreed with me on "chat" about causes of problems- in old gear, electrolytic caps are problems waiting to happen. 5 years for the cheapest of consumer gear, 20 for the average life cap, longer for special epoxy sealed e-caps but you have to have an old catalog with the part number in it to find out if you have any of those. Not very likely in gear sold to consumers. None of my $5000 new organs had any long life E-caps. That was more money than a tricked out muscle car in 1968.
Last edited:
Thanks for chiming in John.
I wish I was able to get through to Art as well. Thanks for that information. As I mentioned, Art did sort completely through this preamp about 4 years ago.
I wasn't making any particular assertion as to the quality of the "Wondercaps"...just a little tongue in cheek as to my uncertainty of the situation.
It does seem obvious that if they did require replacement it would be pricey and I'm not sure how I would go about deciding what would be the proper replacements.
Although I would like to be able to just send it back to Art for another checkup, I don't exactly have the resources for a complete rebuild and I suspect it would be quite a while before it returned.
I am trying to take a "if it ain't broke don't fix it" approach...I think in a way Art might have the same attitude...but he would be able to determine what should and shouldn't be replaced through experience and testing.
Do you have any guidance to offer as to what I should do concerning testing the other caps in the preamp...or for that matter any other questionable components in a preamp of this age?
Regards
Kevin
I wish I was able to get through to Art as well. Thanks for that information. As I mentioned, Art did sort completely through this preamp about 4 years ago.
I wasn't making any particular assertion as to the quality of the "Wondercaps"...just a little tongue in cheek as to my uncertainty of the situation.
It does seem obvious that if they did require replacement it would be pricey and I'm not sure how I would go about deciding what would be the proper replacements.
Although I would like to be able to just send it back to Art for another checkup, I don't exactly have the resources for a complete rebuild and I suspect it would be quite a while before it returned.
I am trying to take a "if it ain't broke don't fix it" approach...I think in a way Art might have the same attitude...but he would be able to determine what should and shouldn't be replaced through experience and testing.
Do you have any guidance to offer as to what I should do concerning testing the other caps in the preamp...or for that matter any other questionable components in a preamp of this age?
Regards
Kevin
Which Diodes?
OK...well I'm finally putting together an order at DigiKey for a bunch of stuff I need for various projects and wanted to tag on the replacement diodes for my Modulus.
Unfortunately, I have not been able to figure out any of the specifics about what would be an appropriate replacement for the stock diodes in a Hi Speed/Soft Recovery version.
I have no idea what values to look for, and after searching through my original owners manual and all over the internet for a schematic of any Modulus preamp for a few hours I have come up empty handed.
I've tried to examine the orginal diodes with bright light and a loop but I am unable to make out any markings beyond a "M" which appears to be a Motorola logo.
The only other lead I have is the mention via PM from another member that his Modulus 3A had BYV 28-100 diodes installed from the factory and they would probably be considered an upgrade and safe substitution for my stock diodes. Of course DigiKey doesn't stock them.
Any help you guys have to offer would be greatly appreciated. This is not something I want to take a guess at and screw up. Thanks.
Regards
Kevin
Edit: Did a drill down on DigiKey based on the data they have listed for the BYV 28-100. Wasn't able to get past matching the standard type and voltage rating, as when I got to the average current rectified at 3.5A the BYV made by Vishay is the only one they list and don't stock. I'm not sure how flexible the voltage/current rating is on a device like this in this application, but I figured raising the voltage/current rating as one would with a capacitor replacement might be acceptable here as well. I came up with this...
http://search.digikey.com/ca/en/products/MUR410-TP/MUR410-TPMSTR-ND/2512805
Any reason why this wouldn't be acceptable?...or for that matter going with one with a slightly higher voltage rating? There seems to be a lot more options available for these rated at 4A, and they are described as ultra fast.
OK...well I'm finally putting together an order at DigiKey for a bunch of stuff I need for various projects and wanted to tag on the replacement diodes for my Modulus.
Unfortunately, I have not been able to figure out any of the specifics about what would be an appropriate replacement for the stock diodes in a Hi Speed/Soft Recovery version.
I have no idea what values to look for, and after searching through my original owners manual and all over the internet for a schematic of any Modulus preamp for a few hours I have come up empty handed.
I've tried to examine the orginal diodes with bright light and a loop but I am unable to make out any markings beyond a "M" which appears to be a Motorola logo.
The only other lead I have is the mention via PM from another member that his Modulus 3A had BYV 28-100 diodes installed from the factory and they would probably be considered an upgrade and safe substitution for my stock diodes. Of course DigiKey doesn't stock them.
Any help you guys have to offer would be greatly appreciated. This is not something I want to take a guess at and screw up. Thanks.
Regards
Kevin
Edit: Did a drill down on DigiKey based on the data they have listed for the BYV 28-100. Wasn't able to get past matching the standard type and voltage rating, as when I got to the average current rectified at 3.5A the BYV made by Vishay is the only one they list and don't stock. I'm not sure how flexible the voltage/current rating is on a device like this in this application, but I figured raising the voltage/current rating as one would with a capacitor replacement might be acceptable here as well. I came up with this...
http://search.digikey.com/ca/en/products/MUR410-TP/MUR410-TPMSTR-ND/2512805
Any reason why this wouldn't be acceptable?...or for that matter going with one with a slightly higher voltage rating? There seems to be a lot more options available for these rated at 4A, and they are described as ultra fast.
Last edited:
Hi David,
Yes...I'm sure you noticed in my post that I referred to you mentioning that to me. The only problem is that it seems DigiKey doesn't stock them...or any others from that series with an approximate or higher voltage or amperage rating.
I've tried drilling down a couple of times using the data they list for it, but I never find anything from that Vishay/General series in stock. That's why I was hoping someone would chime in with some feedback on what I am finding.
Here's another example that popped up. Made by Vishay/General...but a different series and rated for higher average voltage and amperage...different in some of the other specs too.
Digi-Key - MUR460-E3/73GICT-ND (Manufacturer - MUR460-E3/73)
Yes...I'm sure you noticed in my post that I referred to you mentioning that to me. The only problem is that it seems DigiKey doesn't stock them...or any others from that series with an approximate or higher voltage or amperage rating.
I've tried drilling down a couple of times using the data they list for it, but I never find anything from that Vishay/General series in stock. That's why I was hoping someone would chime in with some feedback on what I am finding.
Here's another example that popped up. Made by Vishay/General...but a different series and rated for higher average voltage and amperage...different in some of the other specs too.
Digi-Key - MUR460-E3/73GICT-ND (Manufacturer - MUR460-E3/73)