The transformers are definitely all custom. There is mention in the Collins Signal of either Chicago transformer or Stancor providing a lot of their stock in that era. I am thinking the transformers used for t2/3 do not necessarily follow the 26C-1 or 2 designations either. It seems like we are seeing some combos that suggest the transformer change is separate from the model # change.
Surplus store score! Collins 26c and 2x Gilfillan Bros/Bendix filters pics
- Thread starter plumsolly
- Start date
Help Support GroupDIY Audio Forum:
cletus monroe
Well-known member
Hey Dudes,
Just thinking 'bout my baby and google searching "Collins Interstage Transformers", where I find the PSW
posts from Joe and the link back here to one of my favorite places.
Joe is looking into a possible replacement he got off ebay. It's a Collins, I don't know the model #. My plan is to go in this direction: Six hundad dollas is out me pirate budget right now. Joe recommended and I agree, if a replacement can be found that doesn't compromise the unit, sound and cosmetically, put it in there and save up the money for Doc. If not, she sits until I sell off more obscure Free Jazz records to pay for the rewind. If rewind is a go, and we need the same transformer, I'm definitely up for sending him them at once for a possible discount.
Not to publicly display my affection for you Doug, but you are more than generous with your time and knowledge. Thank you for answering all my emails with a wealth of knowledge. When it's all said and done, these three amigos will be creating a triad of limiting power that will surely give James Cameron's Avatar a run for its three-dimensional money! Sorry, got excited.
Just thinking 'bout my baby and google searching "Collins Interstage Transformers", where I find the PSW
posts from Joe and the link back here to one of my favorite places.
Joe is looking into a possible replacement he got off ebay. It's a Collins, I don't know the model #. My plan is to go in this direction: Six hundad dollas is out me pirate budget right now. Joe recommended and I agree, if a replacement can be found that doesn't compromise the unit, sound and cosmetically, put it in there and save up the money for Doc. If not, she sits until I sell off more obscure Free Jazz records to pay for the rewind. If rewind is a go, and we need the same transformer, I'm definitely up for sending him them at once for a possible discount.
Not to publicly display my affection for you Doug, but you are more than generous with your time and knowledge. Thank you for answering all my emails with a wealth of knowledge. When it's all said and done, these three amigos will be creating a triad of limiting power that will surely give James Cameron's Avatar a run for its three-dimensional money! Sorry, got excited.
plumsolly
Well-known member
It's working!!!!!!!!!!! As Doug suggested, I subbed in T6 for T2 and used an old Stancor 15k:80k interstage transformer for T6. I haven't done any really seriously listening yet, but I did listen to a bunch of Etta James through it after I got it running last night, and it sounded magnificent. (Admittedly, it would be hard for "At Last" to not sound magnificent when listened to on one of the first nights of summer on the front porch.) I noticed that R24 (which sets the release time) has drifted from 10 megs to 2 megs. This will most likely be replaced with rheostat anyhow, but I'm wondering if the other original resistors have drifted as badly. I noticed that I have to drive it pretty hard to get it into the limiting range. Its not a problem if I run it through a channel on my console, but it makes gain staging bit tricky if I am coming right out of my interface. I am wondering if it is possible to lower the threshold. The manual says "The signal level in T2 and T3 at which limiting begins is fixed at a pre-determined point by the amount of delay bias in the cathode circuit of V3." Massive thanks to Doug for all your help. I couldn't have done it without you or Prodigy-Pro. Clay, I got your message and I have been meaning to give you a call. I will soon. Your website looks really nice, and the client list is impressive. Is that a Blonder Tongue eq I see?!
Thanks and best, Ben
Thanks and best, Ben
cletus monroe
Well-known member
That is some good news!! Thanks and thanks. Yes it is. Up top where she belongs! I would be interested to know Doug's thoughts on how the transformer change may affect overall sound with respect to the original. Joe didn't replace all my resistors, but he definitely did more than a few.
plumsolly
Well-known member
plumsolly said:
plumsolly said:
So I have been having this problem intermittently while I have been restoring it. I figured I would eventually trace it to a bad switch contact, cold solder joint, loose tube socket contact, etc... I finally did trace it ... to a sketchy secondary on T1. Sometimes it's good, sometimes it's open, and (less frequently) it's in between. I took the transformer out and I can't consistently get it to be good or open; jiggling the leads (usually) doesn't make a difference, it doesn't seem temperature dependent (I thought maybe the slight expansion/contraction of the potting compound could be making it make/break contact), it just works sometimes and sometimes it doesn't... I'm wondering if the problem might be right where the lead meets the coil and whether it couldn't be solved by melting the potting compound and reconnecting the lead without having to unwind the coil.
Best, Ben
plumsolly said:
Just in case the meter is being dodgy(I've had plenty that are glitchy as heck sometimes) have you tried running audio through it (out of circuit) from say the output of a CD player? Does it follow suit- sound then no sound? Is the sound when there normal(full range) sounding?
thejoerusso
Member
- Joined
- Mar 27, 2009
- Messages
- 17
Hey guys, out of curiosity, do you see the inductances of the s228e listed anywhere?
Joe
Joe
plumsolly
Well-known member
thejoerusso said:
I have not, Joe. Sorry.
Best, Ben
plumsolly
Well-known member
So I bit the bullet and bought a UTC ha-101x and now its working great. I am a little dismayed at the low frequency response, so I went ahead and ordered 100uf caps for C1, C3, and C4 hoping to straighten it out some. The manual claims +/- 2db between 30hz and 10khz. I'll post a response chart. I have also been fiddling with attack and release adjustments. For release, I made r24 adjustable, and for attack, I put a rheostat in series with c9, but I wasn't sure which side to put it on, or if it matters; between c9 and ground, or between c9 and t6? Thanks to Doug and everyone for your help. Best, Ben
cletus monroe
Well-known member
Good to hear!
My transformer is sitting on Doc's bench awaiting revival. It will be interesting to see your frequency response graph. When mine is up and running, I will do the same so we can compare.
Let us know what you think of the sound after you've put her in action!
My transformer is sitting on Doc's bench awaiting revival. It will be interesting to see your frequency response graph. When mine is up and running, I will do the same so we can compare.
Let us know what you think of the sound after you've put her in action!
Here's mine, with much larger cathode bypass caps in most places. I also reversed the pri on a limiter transformer, probably T3 (sec, in context), to get polarity the same for bypass and non-bypass. I should reverse that again and compare the high frequency response. Attack between C9/T6. The sound on mine is awesome.
cletus monroe
Well-known member
Hey Doug!
Being color blind, as I be, is a pain sometimes. If my color blind eyes are not lying, it looks like you have a high freq. boost in bypass?
That's cool. My freq. graph pre pending transformer rebuild was similar, but the high freq roll off was much steeper in limiting mode.
Can't show it now because I'm not at my own computer.
Thanks for the post! It'll be another month or so before the "Whitemare" is in action, but when she is I will post my graph as well.
Just got of the phone with Mr. Hoyer and it looks like the reverse engineering and rewind is going to set me back $650. Not cheap, but I'm also not asking him to bake me a cake either. He said the transformer is actually a custom UTC. He also said she'll be as good as new when he's finished. Fingers crossed!
The actual rewind is $350, so, plumsolly, if you decide to get your's rewound in the future, you shouldn't have to pay the rev. eng. fee. Only $300 for the rewind. I'm not sure how much of a difference there is between your UTC and the original, but when it comes to vintage pieces, original is kinda everything to moi. Then again, if I'm having it rewound, it's technically not original so..... PARTY!!!
Being color blind, as I be, is a pain sometimes. If my color blind eyes are not lying, it looks like you have a high freq. boost in bypass?
That's cool. My freq. graph pre pending transformer rebuild was similar, but the high freq roll off was much steeper in limiting mode.
Can't show it now because I'm not at my own computer.
Thanks for the post! It'll be another month or so before the "Whitemare" is in action, but when she is I will post my graph as well.
Just got of the phone with Mr. Hoyer and it looks like the reverse engineering and rewind is going to set me back $650. Not cheap, but I'm also not asking him to bake me a cake either. He said the transformer is actually a custom UTC. He also said she'll be as good as new when he's finished. Fingers crossed!
The actual rewind is $350, so, plumsolly, if you decide to get your's rewound in the future, you shouldn't have to pay the rev. eng. fee. Only $300 for the rewind. I'm not sure how much of a difference there is between your UTC and the original, but when it comes to vintage pieces, original is kinda everything to moi. Then again, if I'm having it rewound, it's technically not original so..... PARTY!!!
cletus monroe
Well-known member
I'm not sure why he said it was a UTC. I might have said a total of 6 words in my 15 minute conversation with Doc. That in no way is a knock on him. I was actually happy to hear him flow from one technical thing I didn't understand to another mixed with his opinions on how "sucky" digital audio sounds compared to analog. Your knowledge on these matters is far, far above my own. You've got me wondering now. He seems up for some convo, maybe if you called him and mentioned that you had been helping me with my 26c, you two men of great knowledge can solve this new mystery. I just don't have the vocabulary to get down to the nitty gritty.
cletus monroe
Well-known member
I emailed Doc and he was kind enough to quickly reply with the following info:
From Mr. Hoyer:
This is a typical unique UTC design, but it could be made by almost anyone, that is, if they knew how to do it. it is not a simple coil and this is not in any known catalog that I know of. I have called UTC many times regarding RCA interstage coils and I get the same answer that the data was destroyed when TRW, the Magnetika took over the bankrupt stock and winding data. Triad is even worse when they got bought out by the Asians. I used to get TRIAD data all the time, but now that they moved back to California, it is a wash and they think their data is SACRED like the old Western Electric data that is locked up in some barn South of Atlanta, Georgia. Got this info from an old retired WECO engineer that sold me a 618B for 25 bucks.
From Mr. Hoyer:
This is a typical unique UTC design, but it could be made by almost anyone, that is, if they knew how to do it. it is not a simple coil and this is not in any known catalog that I know of. I have called UTC many times regarding RCA interstage coils and I get the same answer that the data was destroyed when TRW, the Magnetika took over the bankrupt stock and winding data. Triad is even worse when they got bought out by the Asians. I used to get TRIAD data all the time, but now that they moved back to California, it is a wash and they think their data is SACRED like the old Western Electric data that is locked up in some barn South of Atlanta, Georgia. Got this info from an old retired WECO engineer that sold me a 618B for 25 bucks.
plumsolly
Well-known member
Time for a much belated update. I have been using and enjoying my 26-c for the last few months with no problems. I have a an HA101X in place of the dodgy input transformer and a Stancor 15k:80k for t6. Right now, I have rheostats in place for attack and release controls, but I am thinking of replacing these with fixed resistors - the attack and release controls interact with each other so much that it can be a pain to find what you want, and I have found a setting I like that I have been leaving it on. I am still deciding what to do about that. I am a little disappointed with the low frequency response: the manual claims +/-2db form 30 to 10k. Here is a plot of mine:
I think this is with limiting engaged, but with the test signal below the threshold. It looks pretty similar to the frequency response chart EMRR posted for one of his 26-cs - so I may not be able to do any better than this as far as the low end goes. I am currently in the process of making some adapters to mount my new transformers more permanently in place of the old ones. So I have them pulled out right now, and I thought I might as well measure them before I put them back in to see if they are having any effect on my frequency response. I am not sure, though, how to properly interface to the transformers' impedances to run the test- can I just make pads to do this on the way out of the transformer? - what about the way into the transformer? Any other suggestions for looking into the low end would be appreciated. Thanks to Doug and everyone for helping me get it this far. -Ben
You look +/- 2.3 dB. Pretty close to stated response.
Many of these sorts of limiters smush and smear out the bottom, even when they measure flat, so consider that factor in future observations and changes.
My response gets better in bypass, which removes the two interstage transformers used in the limiting network.
You've replaced the input with something that is probably better than original, so I think it's safe to assume the output amp interstage and output are the main contributors. T6 won't affect response, only what freq affect limiting.
If you've made the electrolytic cathode bypasses in the audio path much larger (excepting V2 which is designed for high boost; that way in both versions?), and kept bypass on 6R7 small so it passes less lows in the side chain, then adding feedback in the output amp is the most obvious option.
I don't find a need in mine, but if I did, I'd try 6K6 plate to previous 6J7 cathode. Be sure to choose the correct 6K6 plate of the two, so it's not positive feedback. Start with something like a 1M rheostat, and dial it down while making observations. Response should improve, and it should be obvious when you've gone too far. If it still needs help on the bottom, you can then play with adding a cap to limit low frequencies in the feedback path. If a cap gets added, you may need to decrease the FB to get linear again, or divide the resistance in two to some percentage, and have one of the R's in parallel with the C to limit the amount of low freq rise.
Sorry the input didn't work out. I couldn't get it to fail while it was here.
Many of these sorts of limiters smush and smear out the bottom, even when they measure flat, so consider that factor in future observations and changes.
My response gets better in bypass, which removes the two interstage transformers used in the limiting network.
You've replaced the input with something that is probably better than original, so I think it's safe to assume the output amp interstage and output are the main contributors. T6 won't affect response, only what freq affect limiting.
If you've made the electrolytic cathode bypasses in the audio path much larger (excepting V2 which is designed for high boost; that way in both versions?), and kept bypass on 6R7 small so it passes less lows in the side chain, then adding feedback in the output amp is the most obvious option.
I don't find a need in mine, but if I did, I'd try 6K6 plate to previous 6J7 cathode. Be sure to choose the correct 6K6 plate of the two, so it's not positive feedback. Start with something like a 1M rheostat, and dial it down while making observations. Response should improve, and it should be obvious when you've gone too far. If it still needs help on the bottom, you can then play with adding a cap to limit low frequencies in the feedback path. If a cap gets added, you may need to decrease the FB to get linear again, or divide the resistance in two to some percentage, and have one of the R's in parallel with the C to limit the amount of low freq rise.
Sorry the input didn't work out. I couldn't get it to fail while it was here.
plumsolly
Well-known member
Hey Doug - thanks for the comments.
Best, Ben
So the lack of bass I am hearing might not be completely reflected by the frequency response?emrr said:
Does this look right?emrr said:
Don't even worry about it. Thanks so much for having a look.emrr said:
Best, Ben
