Car ICs: yeah, I would think so too. There are plenty of reasons to make car components and ICs superior to home equivalents: all the problems of home reception plus lots of nasty noise and climate extremes to contend with, only 12V power supply, the aerial is moving and is severely undersized.... speaking of which I remember back in the day when the aerial was external and you had to extend it every time you got in the car and, most importantly, push it down every time you got out,, we got our hands on a huge whip aerial that we were really excited about as it would mean no more broken aerials! We never installed it of course as it was truly massive but I thought it would make for a convenient unidirectional (indoors/balcony) aerial.
Theory: This means different things depending on the person and educational background. For an engineer, Bessel functions would be part of a mathematical course. For a technician, it might just be a reference. For a hobbyist, something to look up. Also you get hybrids: those with a science/engineering university education but not necessarily electrical engineers who might have never had the grounding in the RF theory: EM wave transmission, modulation methods etc.
Theory: This means different things depending on the person and educational background. For an engineer, Bessel functions would be part of a mathematical course. For a technician, it might just be a reference. For a hobbyist, something to look up. Also you get hybrids: those with a science/engineering university education but not necessarily electrical engineers who might have never had the grounding in the RF theory: EM wave transmission, modulation methods etc.
Let's just say you would never claim that 150kHz IF bandwidth was enough if you had ever aligned an FM tuner.
For an even better example of MC1310 deployment see the Tandberg 3100. Full-blown discrete opamp after the decoder, and proper filtering.
For an even better example of MC1310 deployment see the Tandberg 3100. Full-blown discrete opamp after the decoder, and proper filtering.
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That's a fair point.
Do you mean the 3001A? That is a super-tuner - looks gorgeous too. In fact the whole series looks great. I don't think I've ever seen one being sold but then again I wasn't looking for one.
https://www.fmtunerinfo.com/lists.html
mentions the tuners with fully discrete MPX stage. The 3001A is one of them. Lists of tuners per MPX IC used are also compiled. I should have remembered this page. The LM4500 features prominently. The UPC1197 is not mentioned nor are any of its supposed clones.
The Akai AT93 has a fully discrete audio section as well reportedly. No doubt there are many other high-end tuners that do too. I can attest to its sound quality.
Unfortunately I only got to hear it once and not had a chance to do any side-by-side comparisions.
Do you mean the 3001A? That is a super-tuner - looks gorgeous too. In fact the whole series looks great. I don't think I've ever seen one being sold but then again I wasn't looking for one.
https://www.fmtunerinfo.com/lists.html
mentions the tuners with fully discrete MPX stage. The 3001A is one of them. Lists of tuners per MPX IC used are also compiled. I should have remembered this page. The LM4500 features prominently. The UPC1197 is not mentioned nor are any of its supposed clones.
The Akai AT93 has a fully discrete audio section as well reportedly. No doubt there are many other high-end tuners that do too. I can attest to its sound quality.
Unfortunately I only got to hear it once and not had a chance to do any side-by-side comparisions.
Im liking this FM decoder circuit. Is it at all possible to use an alternate circuit in case the split beam tube cannot be reasonably sourced? I had run across a FET version of a pentagrid converter tube elsewhere on the internet and wondered if that could be reworked into a split beam tube?
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You can still find a variety of split beam valves for about a tenner or a bit above that. Of course the cost increases rapidly if you want to make more than one converter and also have spare parts so maybe using the split beam valve is just a novelty thing.
An example of a FET version of a pentagrid converter valve would be interesting to share if you can find it.
Here is a link to the page that contains a schematic:
https://www.antiqueradios.com/marc/1l6.html
What I was wondering is if the middle section of the circuit could be removed so that the last part could be capacitive coupled to the first section. Since the tube from the FM stereo circuit has two pentodes with a common anode, the FET circuit would probably need the last section appropriately doubled.
Look what I just found. As the power supply was inadequate and everything was connected to one regulator I separated sections in 2 x 15V and 1 x -15V with regulator ICs and normal decoupling which it totally lacked.
I recall the display having or causing issues that were solved with this board.
Attachments
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Not exactly up-to-date but David Rich wrote an overview of FM in The Audio Critic with a pretty high level of detail. Look at issue 23 here: https://www.biline.ca/audio_critic/audio_critic_down.htm
Thank you for this!
I should check my message box a bit more often: it seems the link is now defunct but, luckily, I could still retrieve the information from the web archive.
I only just check back on this thread... What is that pcb shown in the photo?
Are you referring to the AT93's power supply? What sort of display issues did you experience?
I read a few of the articles by David Rich. Great reads!
Thank you for this link - very interesting stuff. Plenty to read for weeks.
For the LM4500-based decoder? You can (could) find these fairly easily on the web...
Here's a page on all things Leak (including a couple of mpx chip-decoder schematics).
https://44bx.com/leak/index.html
Scroll down till you see the Troughline links.
I wouldn't poke around in a Troughline (or any valve equipment, for that matter) if I did not know exactly what I was doing. Besides the risk of lethal electrocution, there is also the very real risk of damaging the tuner and a repair of a valve tuner nowadays is not a cheap affair, if at all possible.
My advice would be to build the decoder as an external unit, with its own regulated dc power supply, then connect it to a mono Troughline via its MPX output socket. If you do not possess a mono Troughline with an MPX output there are two options:
- Get a mono Troubhline with MPX output (these are now quite cheap) and buy or build an external mpx decoder unit
- If you have a stereo Troughline, you could check the connection point, from which to obtain the mpx signal, on the schematic (although it should be fairly obvious to find by inspection: if it is not, then you have no business poking inside the Troughline). Having said that, replacing the decoder inside a stereo Troughline involves hacking: why do that to a poor old radio? They do sound great in mono anyway.
Of course, you can always wait for one to be sold on ebay with a new decoder already provided/fitted. These do appear from time to time (every one or two years) but they invariably cost a lot more.
I am sorry if this is as helpful as you might have hoped but it is better to be cautious when dealing with electricity - especially with high voltage devices.
It is long ago but the power supply was mediocre. It fed too many sections so I split it up with a few regulators one for each section. I photographed the emptied original PCB and edited it to my likings. It was successful. Akai had a silly habit that time by not using any decoupling of supply lines.
I think the display flickered with the original PSU.
After posting I realised you were referring to a TL III stereo!
The link I posted still applies, together with a TL III schematic (he has the schematics for the TL II and the TL III stereo if you browse around the site a little).
The caution still applies too of course!
Thank you very much!
It just goes to show: even on a fairly pricey tuner, there is always some cost cutting hidden somewhere. I wouldn't expect that to be in the AT93's psu though!
How do you rate the AT93 anyway (both before and after the modification)?
After it was very good but I liked Yamaha T80 better (I think). Its original PSU was maybe not even mediocre but plain bad. Totally out of line when looking at the tuner itself. AFAIK it had only one non decoupled Zener/pass transistor combo to feed the complete tuner. I made that film, edited it old school method and added a few 7815/7915 (forgot the purpose of the 7915 but possibly only a Zener diode was used to create -15V) with necessary heatsinks and decoupling caps and modded several AT-93. It was 1994 so 31 years ago 😊
The transformer needed a heatsink! This was a factory mod.
The transformer needed a heatsink! This was a factory mod.
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There is no such thing. There is III or Stereo. Not III Stereo.
The post you are replying to is two years old. I have already provided the information required to the poster. And you can indeed fit the decider inside, exactly where the old one was.
That must be a first! Especially if fitted from the factory... I think I opened mine to have a peek inside but only temporarily...
I thought you meant the Yamaha T-85 initially. So the, the AT93 has at least 3 Yamahas to contend with...
Sure, sure... I was (I am) too lazy to check. I only meant to say there is a TL II circuit with or without an MPX output and a TL III circuit with or without an MPX output.
Or maybe even that is not correct and they just have a different fascia or a different circuit or both, with or without an MPX output. I know I have a TL (II ?) with the dacron fascia and a fitted decoder. The circuit is neither TL II nor TL III. Maybe it is a TL Stereo. Go figure... I've seen all sorts. The only think that I can surmise is that maybe some older TLs were sent back to the factory for modifications and conversion to stereo.
Yep, if you make it the same size and have the skills, sure you can. The site I linked shows a photo with a new and an old pcb for the decoder.
I should check the replies more often and more carefully. Last time I checked it seems I only noticed the last reply and went off to read the David Rich articles and then forgot about the other replies.