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 Post subject: H H Scott transistors(The saga continues)
PostPosted: Oct Sat 19, 2013 7:20 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 399
Location: far western end of Maryland...21561
Working on a HH Scott "hybrid" (transistors and nuvistors) FM tuner. Scott's service info gives the transistor part numbers as a Scott specific part #; the numbers below are the part number, NOT the location designation on the schematic.

QA1
QA2
QRF2
QA-10

Somewhere, I hope, someone has figured out how these Scott numbers cross to more usable numbers. I would like to use the intended equilivant, rather than something that "sorta works"

Any help on this would be greatly appreciated

Thanks

Andy


Last edited by AB on Oct Mon 21, 2013 6:53 pm, edited 1 time in total.

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 Post subject: Re: H H Scott transistors
PostPosted: Oct Sun 20, 2013 12:37 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Rochester NY USA
What model? If it's in Sams, they may have listed equivalents.

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 Post subject: Re: H H Scott transistors
PostPosted: Oct Sun 20, 2013 2:07 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 399
Location: far western end of Maryland...21561
Tom

The tuner is a 312 ( the early one with no suffix letter). The transistor of immediate concern is a "QRF2" . There are 5 of them in the IF string and, based on swapping them around, one is a problem. There are no markings on the transistor.

I don't have the SAMS, so don't know if it's in there or not, or if SAMS has it. I'm finding there is not much info out there on HH Scott gear. The Scott "service manual" just lists the Scott number

Again, any help, suggestions would be appreciated.

Andy


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 Post subject: Re: H H Scott transistors
PostPosted: Oct Sun 20, 2013 3:35 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 16749
Location: Albuquerque, NM 87123
The QRF2 crosses to an NTE128. Is the transistor a round metal type? The Q-RF2 is listed as a NTE123AP (plastic case)

No listing for the QA1 or 2. The QA10 is in RCA's SK book as a SK3024.

Hope this helps.


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 Post subject: Re: H H Scott transistors
PostPosted: Oct Sun 20, 2013 2:25 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 399
Location: far western end of Maryland...21561
Johnnysan

Thanks, it helped a lot! The NTE123AP would be the right function; I then did some more cross referencing and found that a 2N3904 would cross...and I had 10 of them. A little swapping around an the thing works again.

The tuner did work, and is going to get it's pile of Callin electrolytic caps replaced, but it suddenly died. Based on the symptoms it was the IF strip, I replaced the Callin caps related to that but no joy....the transistor fixed it.

In my travels after your note did find the cross reference search on the NTE site...very useful as it turns out.
http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/


The Scott is one heck of a tuner...and it does have TUBES (4 Nuvistors)

Thanks for the help

Andy


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 Post subject: Re: H H Scott transistors(The saga continues)
PostPosted: Oct Mon 21, 2013 7:04 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 399
Location: far western end of Maryland...21561
The more I work on this thing, the better it gets. However, I have reached a dead end on a cross reference on what HH Scott identified as QA-2 ( it matters where you put the hyphen) transistors. There are two transistors in those locations now, one with a case so oxidized that any ID is long gone, the other is obviously a replacement, with no ID at all. I would really like to replace them but can find no cross reference anywhere.

So:

1)If anyone has a Scott 312 (no suffix) tuner, or perhaps the kit version (LT-112) where these have been replaced or have any ID on them ( they are in position Q-6 and Q-8 on the chassis and the schematic) it could be helpful.

2) Is there a HH Scott forum out there anywhere ?; I found reference to one that apparently used to exist but it's dead.

Thanks

Andy


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 Post subject: Re: H H Scott transistors(The saga continues)
PostPosted: Oct Tue 22, 2013 12:39 am 
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Location: Fernandina Beach, FL
AB wrote:
The more I work on this thing, the better it gets. However, I have reached a dead end on a cross reference on what HH Scott identified as QA-2 ( it matters where you put the hyphen) transistors. There are two transistors in those locations now, one with a case so oxidized that any ID is long gone, the other is obviously a replacement, with no ID at all. I would really like to replace them but can find no cross reference anywhere.

So:

1)If anyone has a Scott 312 (no suffix) tuner, or perhaps the kit version (LT-112) where these have been replaced or have any ID on them ( they are in position Q-6 and Q-8 on the chassis and the schematic) it could be helpful.

2) Is there a HH Scott forum out there anywhere ?; I found reference to one that apparently used to exist but it's dead.

Thanks

Andy


Hi Andy,

I did check and I have two Scott 312 tuners and only the LT-112B and LT-112B1. Both 312 tuners have RCA transistors labeled QA-2. Some are so corroded that they are almost impossible to read. I didn't look inside of the LT-112B tuber.

The HH Scott Forum was vacuum tube only and it has been non-functional for quite some time now. At least if you need schematics for vacuum tube items, they are still working.

I don't have a schematic for the 312 tuner.

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 Post subject: Re: H H Scott transistors(The saga continues)
PostPosted: Oct Tue 22, 2013 6:32 pm 
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Posts: 18781
Location: Utica, NY 13502 (USA)
Hi Andy,

I'm glad you mentioned that the LT-112 series is the kit version of the 312 series.

I have an LT-112B kit and the complete 80 page construction/operating/service manual. I have to think there isn't much difference in the circuitry of your 312 factory wired unit beyond having a solid state front-end and that it uses PC boards instead of being hand-wired.

Q301, Q302 and Q303 on the IF board are listed as Fairchild SE-1001 or Micro-Electronics ME-1001.

Q304 and Q305 are listed as SE-3001 or ME-3001. These are used as limiters and must have slightly different characteristics than the others.

The audio circuits use a 2N3702 in the input stage (Q5, Q7) and either a 2N2924 or a 2N3710 for the output stage (Q6, Q8)

Hope this helps.

Dave


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 Post subject: Re: H H Scott transistors(The saga continues)
PostPosted: Oct Tue 22, 2013 9:46 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 399
Location: far western end of Maryland...21561
Don and Dave

Thanks for the info, this is already turning out to be a really good, sensitive tuner with a lot more to be done to it so any info helps. I'm surprised by the lack of into out there on Scott gear ...hard to say why.

I'm also enjoying the fact that it's the early one with Nuvistors and hard wired...none of those sissy FET's and printed circuit boards.

Andy


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 Post subject: Re: H H Scott transistors(The saga continues)
PostPosted: Oct Thu 31, 2013 6:55 am 
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Joined: Jul Thu 11, 2013 1:18 am
Posts: 18
Location: Providence, RI
I don't mean to hijack the thread but I have exactly the same issues with the same 312 tuner, NUvistors , transistors and hand wired.

My unit is missing some of the transistors and I have had no luck in finding a schematic and or service data.

Any info you folks are willing to share would be greatly appreciated. Andy, I am happy to post photos if that helps with your project.




Best regards

Kevin


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 Post subject: Re: H H Scott transistors(The saga continues)
PostPosted: Oct Thu 31, 2013 12:30 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 399
Location: far western end of Maryland...21561
Kevin

Transistors:

the QRF-2's in the IF strip can be replaced with 2N3904 (Mouser or where ever) and they work great

I have seen stuff that suggests that the QA1 can be replaced with NTE-160..but I have no idea if it works.

I have tried any way I can think of to find a sub for QA2 and so far zip


"tubes tubes tubes" (Gary in Maine) has nos Nuvistors if you need them.

Also.. you need to replace all the (Callins in my case) e-caps and the filter caps. About 1/2 of mine tested bad and they are a time bomb. I restuffed the filter cap can. Some of the small e caps are "interesting" to get to but it can be done.

At this point my 312 works great. Like most of them it does not have a case but I have a nice piece of cherry........


Andy


Last edited by AB on Feb Thu 13, 2014 1:12 pm, edited 1 time in total.

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 Post subject: Re: H H Scott transistors(The saga continues)
PostPosted: Nov Sat 02, 2013 5:05 am 
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Joined: Jul Thu 11, 2013 1:18 am
Posts: 18
Location: Providence, RI
Andy,

Thanks' much for the link to the schematic and the other cross reference info. With my work schedule these days, it will probably be another month before I can continue on my 312. Once I start, Caps will definitely be at the top of the list along with the transistors.

I believe I read somewhere that these hybrid 312's were broadcast grade and that early FM networks utilized these for rebroadcasting. Perhaps some of the Scott experts here can shed more light on this unit.

Thanks again for the info and keep us posted on your rebuild.

Regards

Kevin


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 Post subject: Re: H H Scott transistors(The saga continues)
PostPosted: Nov Sat 02, 2013 11:29 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 399
Location: far western end of Maryland...21561
Kevin
see

http://www.lacieg2s.ca/w3terra/ols/scott312.htm

also, keep in mind some of the e caps are in the signal path. As such you need to replace them with caps that will give the sound a hint of smokey oak flavor, with a fruit aftertaste and only install them during the full moon..............or anything from mouser installed with the polarity correct and good soldering should work

Andy


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 Post subject: Re: H H Scott transistors(The saga continues)
PostPosted: Nov Sat 02, 2013 1:28 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 18781
Location: Utica, NY 13502 (USA)
km5881 wrote:
I believe I read somewhere that these hybrid 312's were broadcast grade and that early FM networks utilized these for rebroadcasting. Perhaps some of the Scott experts here can shed more light on this unit.


Image

This is a picture of my rack-mounted and not-pretty HH Scott 310-DR which came from an AM station in upstate NY. It was used in conjunction with the Northeast Radio Network's program called "Weather Roundup" in the late '50's and '60's. This program linked many stations across New York and New England with each giving hourly updates of weather conditions in their areas. The network was based in Ithaca, NY and used the FM stations, which were originally part of the Rural Radio Network started by the GLF farmers cooperative in 1948, as the audio link. Stations which were part of the network needed a highly sensitive and stable tuner to receive the broadcasts from one of these stations.

Image

I believe Scott used the term "Wideband FM Broadcast Monitor" on their consumer-style tuners as well. The 312 may, indeed, have been used in broadcast situations as well.

Dave


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