Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Dec Mon 18, 2017 3:52 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 15 posts ] 
Author Message
 Post subject: Sentinel 285p....
PostPosted: Jul Thu 21, 2011 10:28 pm 
Member

Joined: Sep Wed 29, 2010 10:01 pm
Posts: 256
Location: virginia
i picked this up at a junk store in the middle of nowhere va along with 2 other radios, an emerson 425 and an electronics laboratories 2701.
i was amazed at the amout of caps in this little portable radio. where many like this? i almost didnt repair it when i saw how many caps i needed. 15 wax paper, 4 electrolytics, and a few resistors.
it does play quite well and picks up 12 am stations which is alot for this area.
Image
By flyingturns

Image
By flyingturns

Image
By flyingturns

Image
By flyingturns


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Jul Fri 22, 2011 12:08 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 25769
Location: SoCal, 91387
Yeah, that capacitor count is not surprising; I've repaired more than one portable from that era that had a similar number.

But look at it's performance because of that type of circuit design.

Beautiful set, BTW.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Jul Sat 23, 2011 5:17 pm 
Member
User avatar

Joined: Oct Wed 14, 2009 6:36 am
Posts: 5829
Location: New York USA
I am re-capping an Olympic portable, and they needed capacitors to bypass the filaments to keep the stages isolated, there are no cathodes (in my set). It was meant for vacations in rural areas, so they added a tuned RF stage and everything for long-range reception. These portables can be great performers.
Don

_________________
Diode Don, all problems rectified.

Someone with less knowledge than I had been in there before ....


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Jul Sun 24, 2011 4:37 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 7473
Location: Beaver Falls, PA. USA
I have its prewar brother, the 276P, also full of capacitors. The design engineers needed all that bypassing when they put the tube filaments in series, as was commonly done on the "three-way" radios. Many of them had a tuned RF stage, or an extra IF stage, adding to the complexity.

_________________
Tim KA3JRT


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Jul Sun 24, 2011 8:42 pm 
Member
User avatar

Joined: Oct Wed 14, 2009 6:36 am
Posts: 5829
Location: New York USA
The schematics on Nostalgiaair show #44 pilot lamps with 75 ohm shunts but there would not be enough current to light a #44, as they use a 117Z6 rectifier.
Don

_________________
Diode Don, all problems rectified.

Someone with less knowledge than I had been in there before ....


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Jul Mon 25, 2011 1:57 am 
Member

Joined: Sep Wed 29, 2010 10:01 pm
Posts: 256
Location: virginia
thanks guys. i didnt know that about the old portables. ive only been doing this for a yr and a half or so. i did one other 'portable', as large as suitcase, about a yr ago. a sears wayfarer. it was a real pain. there were a number of caps under the tuning drum this radio uses.
probably why it sounds so nice as well.
Image
By flyingturns


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Jul Mon 25, 2011 9:33 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 25769
Location: SoCal, 91387
Generally speaking, better performing radios are that way because they employ a larger component count than run of the mill sets.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Dec Fri 07, 2012 6:42 am 
Member
User avatar

Joined: Oct Thu 18, 2007 11:34 am
Posts: 3527
Location: Port Orchard, Wa 98366
I know this post is a year old, but the Sentinel radios were also made for Coast to Coast stores under the name of Musicaire, which I have (Model ME6). Same Schematic. I found this post as I was looking for My new possession :mrgreen: of the same portable. Its listed in Riders in book 16 pages 11-13 as Sentinel radio.

_________________
Visit our Webpage:
http://antique-radio-lab.forumotion.com/


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Dec Mon 04, 2017 3:39 am 
New Member

Joined: Dec Mon 04, 2017 3:06 am
Posts: 3
Dear Friends, I am new to this forum. Also new to fixing/refurbing old tube radios ( I do have some modest understanding of electronics).
I just picked up a Sentinel 285p radio that I am very excited about and would like to bring it back to life(have not plugged it in yet).

I understand that recapping these instruments are a must. Looked to me that there are three different types of caps are in this unit.
There are two large sized electrolytic ones among the tubes. Then there are these Bakelite looking little bricks with color coding dots on them. Finally, the cylindrical ones. Would somebody please point me to some reading material on which ones need replacement, what to replace them with, etc.
Thanks a lot.


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Dec Mon 04, 2017 8:59 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 25769
Location: SoCal, 91387
Welcome to the board, and congrats on bagging a Sentinal 285p; they're great looking period radios!

Your first replacements should be the Electrolytic filter caps. Once you've done that, it should be safe to power the set up temporarily, to see if it plays. The values, mFd and working voltage, would be printed on the side. The same for the wax caps. Our member Sal has an ad on the right side of the page, and carries everything you need, as one source.

Next step would be to replace the cylindrical wax caps, maybe 2 at a time, testing after each. That way, if you mis-wire, it's narrowed down to just the last two. Generally, mica caps (the square one's with dots) don't need replacing, and it's best to leave them alone.

Please report your progress, and post a scan or two.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Dec Tue 05, 2017 3:14 am 
New Member

Joined: Dec Mon 04, 2017 3:06 am
Posts: 3
thank you very much for your response with the pointers.

So the first attack will be on the electrolytic filter caps...
These Al canned caps house actually two caps each, right? One of them is 50microF and 5microF, the other is 2x40microF.
Can these be replaced by individual caps? I do not recall ever seeing these doubled up versions...

Clearly we cannot replace with "authentic" (read: historic) parts, they would be just as much out of specs. The goal is to get them running with as little departure from original design/parts as possible, correct?

So as long as the voltage and capacitance values are met, it should be good to go...?

The cans of these caps are sitting on a bakelite looking bases which are riveted to the metal base carrier. Probably I should keep the bakelite pieces to keep the solder tabs... Looks like that even these two sets of caps will be quite a hassle to take our and replace...

I tried to include here a picture of part of the schematics but I could not... what is the mechanics of including images?
Thanks.


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Dec Tue 05, 2017 3:52 am 
Member
User avatar

Joined: Jan Tue 31, 2012 1:55 am
Posts: 2958
Location: Mountains of Mourne. Ireland.
Riders schematic for Sentinel 285P can be found here...
http://www.nostalgiaair.org/Resources/


For a service manual with pretty pictures... :)
Sams Photofact service manual Set-6 Folder-27 October 1946
can download from radiomuseum.org for free
https://www.radiomuseum.org/r/sentinel_285p.html
Click a schematic page from the right-hand scrolling window, then again in the main center window.
Bottom four pages are Sams.
Each page will be emailed to you immediately.
You can only download three pages a day + up to a maximum of ten every 30 days.

If you experience any downloading difficulties... see this→ viewtopic.php?p=2571007#p2570117
pdf attachments are not visible in junk email folders.


For a clear copy...
ebay $6.25 https://www.ebay.com/itm/SENTINEL-285P- ... g#shpCntId
What it looks like... different listing. Lol
image: https://i.ebayimg.com/images/g/LdQAAOxy ... -l1600.jpg
image: https://i.ebayimg.com/images/g/stoAAOxy ... -l1600.jpg
image: https://i.ebayimg.com/images/g/ycMAAMXQ ... -l1600.jpg

Greg.

oh... Posting photos to a forum thread.
The skinny: viewtopic.php?p=2717120#p2717120


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Dec Tue 05, 2017 4:31 am 
New Member

Joined: Dec Mon 04, 2017 3:06 am
Posts: 3
Great resources, thank you Greg.
-kosatomi


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Dec Tue 05, 2017 4:59 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 25769
Location: SoCal, 91387
kosatomi wrote:
So the first attack will be on the electrolytic filter caps...
These Al canned caps house actually two caps each, right? One of them is 50microF and 5microF, the other is 2x40microF.
Can these be replaced by individual caps? I do not recall ever seeing these doubled up versions...

Yes, SOP is to disconnect the wiring going to each of the solder lugs, and connect them to each positive lead of two discrete Electrolytic's.
You can then tie each Electrolytic's negative lead to circuit ground, usually a lug on the bottom of the can. There should be one or more symbols on the 50/5 mFd can, next to each value, and then again underneath, to identify which lug connects to which capacitance value. Of course the 2x40 mFd wouldn't need designations.

kosatomi wrote:
Clearly we cannot replace with "authentic" (read: historic) parts, they would be just as much out of specs. The goal is to get them running with as little departure from original design/parts as possible, correct?

Yes. Some collectors however do go to the point of "restuffing". With the vertical metal cans, it would require slicing them off at the base above the chassis, removing the originals, and replacing with new discrete caps. A cable saw is an excellent tool for this.

AFA the wax caps, new ones can be inserted into them as well, if you really want to make it authentic looking, but really, whose gonna be removing it from it's cabinet and inspecting under the chassis?

kosatomi wrote:
So as long as the voltage and capacitance values are met, it should be good to go...?

Correct. Aside from the Electrolytic's, most new non polarized caps are rated at 630 volts, largely well beyond what's required.

kosatomi wrote:
The cans of these caps are sitting on a bakelite looking bases which are riveted to the metal base carrier. Probably I should keep the bakelite pieces to keep the solder tabs... Looks like that even these two sets of caps will be quite a hassle to take our and replace...

Don't even mess with trying to remove the cans. Just electrically replace them underneath, as described above. Leaving them in place maintains cosmetic authenticity.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


Top
 Profile  
 
 Post subject: Re: Sentinel 285p....
PostPosted: Dec Wed 06, 2017 4:26 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 810
Location: Detroit, Michigan
I have one of these radios, not yet working or restored, but had a question about it. Good shape, but I have to have a new leather handle and rear door leather opening piece made for it. I noticed in the schematic that one tuning cap gang is before the rf tube. There is no tuning cap gang before the mixer tube, but there is the oscillator gang. The set has only a two gang tuning cap. Just wondering, is this a tuned rf setup, or am I all wet here? It looks like there is no tuning capacitor tuned input to the mixer, like there would be on a set without an rf stage. Confused :?

_________________
'If the women don't find you handsome, they should at least find you handy.' -Red Green


Top
 Profile  
 
Post New Topic Post Reply  [ 15 posts ]  Moderator: sofaslug

All times are UTC [ DST ]


Who is online

Users browsing this forum: FSEradnut70, jonnyastro, tasar and 22 guests



Search for:
Jump to:  


















Privacy Policy :: Powered by phpBB