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Reviving a Dynaco FM 5 or 6

67.253.54.149

Posted on September 20, 2016 at 09:14:24
Posts: 573
Location: Maine
Joined: August 16, 2011
Hi, I would like to go thru a Dynaco FM- 6 that I have laying around. I can replace caps and resistors and clean switches and contacts. I have the right manuals. I guess my question is; What would be a kind of (check list) of tests assuming the tuner has been pre-aligned to get an FM-5 or FM-6 singing again. Are there any problem areas that you guys might know? Thanks, Mark Korda.

 

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Lots of signal strength will be good., posted on September 21, 2016 at 14:15:11
Timbo in Oz
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;-)


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Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: "assuming the tuner has been pre-aligned", posted on September 23, 2016 at 13:11:39
1973shovel
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Depending on which caps and resistors you replace, your "pre-alignment" could easily be trashed once certain components are replaced.

Also keep in mind that indiscriminately changing carbon resistors to, say, metal films in an RF circuit could cause you performance issues. Replacing parts in tuners isn't to be done casually, except perhaps for the power supply and output stage.





Take note of paragraphs two and three.

Good luck with it.


 

RE: "assuming the tuner has been pre-aligned", posted on September 23, 2016 at 20:52:43
hahax@verizon.net
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I can back you up. A friend who designed from scratch told me the front end of a tuner can be fouled up by going to 'better' classes of resistors.

 

Good to know, thanks! (nt), posted on September 24, 2016 at 14:32:59
1973shovel
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RE: Good to know, thanks! (nt), posted on September 24, 2016 at 15:40:28
Posts: 573
Location: Maine
Joined: August 16, 2011
Hi, thanks all you guys for the info. For what you told me I know I don't have the skills to tackle the alignment or any major diagnosis. I like my FM-3 but as I said before somewhere here AM where I live has better stations. I have a Dyna 6 which has AM and I got the urge to hook it up. If you know any good tuner fixers out there I'd love to know. Thanks for the right direction...Mark Korda

 

Hi Mark, posted on September 25, 2016 at 09:05:15
1973shovel
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Since you have the manual for the AF-6, you're a step ahead. I just took a quick look at an on-line manual for the AF-6. Some of the numbers on the schematic were somewhat blurry, so keep that in mind with what I'm about to say, and double check your schematic. Perhaps someone else has a clean copy and can chime in too.

If I had an AF-6, I would replace C84 and C85, listed as 500µF, 25V caps, and C86, listed as a 250µF, 25V cap. These caps appear to be the main electrolytic smoothing caps in the power supply, and I'd be replacing them simply because of their age. Note the polarity of C85.

It also looks like R95, R96, and R97 are B+ power supply resistors (again, these numbers are somewhat blurry), and if they are, I'd change them to a film resister (if they're currently carbon comp) to quiet the power supply down.

In the output section, I'd certainly replace C69 and C72, both 1µF, 25V output coupling caps, which are directly in the signal path. If I could fit film caps, great, but I'm betting there's not room. If not, I'd try Elna Silmacs. Some don't care for them, but none other than Nelson Pass has high praise for their sound as a coupling cap. Nichicon ES would be another option I'd consider, if space is a consideration and you don't care for the Silmacs.

Also in the output signal path are R71, and R79, both 1000 Ω. You might consider replacing them (assuming they're carbon comps), but some like the added warmth they bring.

One good thing is that if AM reception is your main goal, according to the manual you can align the AM section yourself, without instruments. Consult your manual for full instructions.






This is where I'd start, then go from there if I had any other issues. Good luck with it.

As it says under the header at the top of this Asylum, "Thank God for the radio!"


 

RE: Hi Mark, posted on September 25, 2016 at 15:51:08
Posts: 573
Location: Maine
Joined: August 16, 2011
Hi Shovel,
Thanks so much! Thats an answer and a half to my question. You went above and beyond! You also answered another question, your the tuner man.
Last night I got my FM-3 going. This might be the second time since it was lying dormant for 3 years that I turned it on for a while. It's in my bedroom with a Dyna 70. They make nice night lights as well as sounding real good. The FM-3 was pulling every thing in like nothing before. I did notice in the FM-3's rebuild a pc board with a small army of caps all lined up near the tuning eye tube.
Shovel, do you think that the caps needed more time to reform?....Also, I learned a new word,(dope slap) which I'd like to send one via e-mail to the B&O speaker finder guy...if you know what I mean. Thanks for the info....and if you ever hang out the tuner man shingle I'd like to be your first customer....Mark K.

 

RE: "your the tuner man", posted on September 26, 2016 at 06:41:41
1973shovel
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Thanks Mark, you're too kind. But actually I'm not the tuner man.

I'd never looked at the AF-6 schematic before, so I thought I'd check it out. What I did was exactly what I suggested to you in my first reply, which was to stick to the power supply and output section as places to start.

I wouldn't know the first thing about improving the radio frequency performance of a tuner, and don't have the equipment to align one. You might want to contact inmate Mike Samra. I believe he does tuner alignments, but you'd have to check with him.

The caps in your FM-3 could need some more time to settle down, especially after not seeing power for three years. Give that thing plenty of ventilation too, they run hot!

Speaking of caps, the nicest upgrade I made to one of my FM-3 tuners was to change the two output caps (C82 and 83) to 0.1 µF Russian FT-3 Teflon capacitors. They're about two inches long, and you have to mount them vertically, so they just barely fit under the FM-3 cage. You'd need something to insulate the "top" lead from the cage, just in case it touches. I think I used electrical tape or heat shrink. They sound exceptional in the Dynaco FM-3, and are a bargain. I've included a link, if you're interested. No affiliation, of course.

Yeah, the B&O guy. He needs to take a lesson from you as to how to pose a direct question. He asks a vague, open-ended question, then gets his panties in a twist when he doesn't get the type of answer he wanted. It takes all kinds.

Have fun with your tuners.


 

RE: Hi Mark, posted on September 26, 2016 at 18:00:57
hahax@verizon.net
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You reminded me that a friend, now long gone from audio, modded my FM3 decades ago. He made some changes that he said mimicked the Marantz 10 front end which I unfortunately can't describe. But I also recall he changed solid state diodes in the circuit for tube diodes which he said made a nice difference in sound. I think he replaced all the diodes but one because it was a difficult mod he didn't have time for in one weekend.

 

RE: Hi Mark, posted on September 26, 2016 at 21:29:51
Posts: 573
Location: Maine
Joined: August 16, 2011
Hi Shovel, Timbo and Hahax too.
A few years ago I bought a Dyna FM-3 for 200 dollars. It was from a site on the computer which was dedicated only to the FM-3. They had one for sale that contained all their mods.They aligned it too. I'm trying to re find that site. They were the first to provide an optional black faceplate before I saw them for sale on Ebay.
Shovel, I'm not a big believer in break in times but the more time I have had the FM-3 on the better things are sounding....cap loading we talked about. One thing that looks different from stock is this little pc board cut out on one end for a tube right behind the tuning eye. I think Sheldon Stokes might have come up with these as I've seen them alot in images of the FM-3 on a Google search. It looks like a little army of caps all the same size lined up for duty, nothing like stock.
On the FM-6. Mike Samra's a great guy and freind but I wouldn't want to take his time up with an AM tuner as a normal person might just get a cheap radio to listen to AM. It will be added to my list of projects. Shovel from what you told me if I go slow an methodic I think I can make a stab at trying to get the FM-6 back on track. If I had a MacIntosh 78 or a nice H.H. Scott tuner then I wouldn't hesitate to get Mike S. on it. Shovel, I will copy your instructions and staple them as an addition to the manual. Even if I can't get to it tomorrow I do want to get that tuner going and your efforts will be recorded for me and anyone else that it can help getting a nice piece of gear like the FM-6 or FM-5 going.
Shovel, someone spared me administering the dope slap on the B&0 speaker guy. He down right blasted him! I forgot his name but I'd like to give him a nice (non-dope slap) on the back for doing so.You tried to help him and he gave you a Pearl Harbor job!
Take care and keep those stories and the info coming...thanks ...Mark K.

 

The AM section in the AF-6 is actually reputed to be pretty good, posted on September 27, 2016 at 05:11:17
mhardy6647
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I can't vouch for that though; the AM in mine is Bjorked ;-)

I was going to look into the contacts in the "air variable" tuning capacitor, but i was... dissuaded... by all of the stuff decorating it. No simple "pop off the shield and have at" in the AF-6.

Maybe someday.

DSC_9819

Yeah, my Dynaco electronics collection is pretty motley. The SCA-35's nice.
all the best,
mrh

 

AM? IS worth it down here, posted on September 27, 2016 at 13:38:14
Timbo in Oz
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But only for folks who listen to the national public broadcaster.

Radio National from our own ABC, like the BBC?

Wide audio bandwidth and NRSCA Eq, add a 9khz notch filter and you are good to go.


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Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: "I'm not a big believer in break in times", posted on September 29, 2016 at 09:02:55
1973shovel
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I'm from Missouri too, Mark, but it sounds like you've just proved "settling in times" to yourself, via your FM-3. I've had similar experiences with other components.

Without a picture, I can't say for sure what your "little army of caps all the same size lined up for duty" is for. Are there any resistors on the board? If so, given its placement, it might be David Berning's corrected de-emphasis circuit, described below in an FM-3 modification article.










I believe Sheldon Stokes marketed (or perhaps still does) this circuit on a board for the FM-3.

I found a post from back in July on the Ghost Town formerly known as the Asylum's Dynaco-Doctor Forum. You might take note of how many bad electrolytic caps the author found. (link below)




 

RE: "I'm not a big believer in break in times", posted on September 29, 2016 at 18:16:53
Posts: 573
Location: Maine
Joined: August 16, 2011
Hi Shovel, thanks for all the info.
After a long search on the net I could not find the FM-3 tuner site that did my FM-3. I did go on Dynaco FM-3 images on Google and compared my little army of caps board to the pics. My board is a Chauncey/Epperson pc mod if your interested.It's exact.
Shovel, I have forgotten the procedure to add a picture to what I write. I have Windows 10 and cut and paste is not working for me like it used to. If you know real quick I'd love a lesson. I can find the pictures but have trouble posting them to my messages...thanks Shovel.
Shovel, I'm from Maine all my life. The closest I ever got to Missouri is being a fan of the Kansas City Chiefs when I was in the seventh grade. I still have a shirt 86, Buck Buchanan I saved up for, 1970.
Shovel, before I go I have some various Heath tube tuners I'd like to get your thoughts on. Maybe I shouldn't stray from the topic though. You are ( Tuner Man), you can't help it, you know your stuff. Thanks for sharing...Mark Korda.......PS. What about the Outlaw Josey Wales, Clint Eastwood, when he gives the pursuit a (Missouri Boat Ride).....

 

RE: "I'm from Maine all my life.", posted on September 29, 2016 at 19:33:01
1973shovel
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Shovel: "I know a girl in Maine"
Mark: "Bangor?"
Shovel: "No, we're just good friends"

Bah Dump bump!

Ok, that's enough of that. I've never been to Maine. I got close this summer (Laconia NH). We were supposed to ride up into Maine, but it didn't happen. Next year, hopefully.

The only method I know to add a picture to your post on the Asylum is to first download it to your computer.

1. Right click on the picture you want to save.
2. Choose "save picture as" from the menu.
3. Save the picture to your computer. I use my desktop for temporary pictures.
4. At the bottom of the Asylum "Post a Message" box (below where you write text) are several choices. One is "Upload Image" browse button.
5. Click "Browse" and find the picture on your desktop (or wherever you saved it) and click on it. When you preview message, the picture will upload.

More information at the link below.


 

RE: "I'm from Maine all my life.", posted on September 30, 2016 at 04:01:31
Posts: 573
Location: Maine
Joined: August 16, 2011
Hi Shovel,
Thanks so much for those (easy) instructions. They are game changing for me. The Windows 10 book for dummies couldn't do that.
Great joke! I never heard that one, really. Bangor is about 150 miles north from me and Boston 100 miles south. I'm outside of Portland now....Old Orchard Beach. In the summer it's a tourist town with a lot of Canadians from Quebec around.
Later tonight I will practice the new procedure you have taught me....thanks again Shovel....Mark.

 

RE: "I'm from Maine all my life.", posted on September 30, 2016 at 10:10:53
Posts: 573
Location: Maine
Joined: August 16, 2011
Hi Shovel, I realize the importance of (Step #5),the preview. I wouldn't want when asking about info for the Heathkit FM-3A mono tube tuner a picture of Nina Hartley getting attached...why...why that may get me booted out of Radio Road.....Mark.

 

You're welcome, posted on October 3, 2016 at 05:28:09
1973shovel
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I'm looking forward to seeing the pictures you post, especially Nina Hartley!


 

RE: You're welcome, posted on October 3, 2016 at 10:03:30
Posts: 573
Location: Maine
Joined: August 16, 2011



Hi Shovel, this is a Down East style cabinet I made with a hand saw, sheet rock screws,barn board and some old weathered pieces of a freinds old lobster traps. The rubber feet are used on a ground fishing boats trawl nets.
I made this a few years ago and have the picture already in my picture file but did write down the procedure you gave me so I can get a picture from the computer and not one I have already.....Ps. If Nina Hartley threw her hat in the ring for president right now it could be an upset land slide!...Mark K.

 

Lobstah Licious, posted on October 5, 2016 at 09:10:35
1973shovel
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I like your tuner's nautical theme. Nice work!


 

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