Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
It's been a year and a half since Mike rebuilt his Pioneer SX-1500TD. I've owned one for a little while longer than that, and used it regularly until it developed audio issues.
I've decided to completely rebuild the audio amp board with all new electrolytics.
This required pulling the board from the chassis...which is mounted in such a manner that the output transistors and heat sink are all mounted to the audio amp PC board.
[Image: http://www.philcoradio.com/images/phorum...TD_001.jpg]
This is a view of the audio amp board from underneath.
Removal required unsoldering and removing eleven wires, removing the metal cage on top covering the output transistors, removing two screws holding the whole thing in place, and pulling it out from the top.
I ordered the parts from Mouser tonight.
I've put this job off far too long. I'm looking forward to getting this one running again. I had previously replaced all of the dial lamps, and it looked good and worked well until it lost one audio channel. It's rated at 58 watts per channel into 8 ohms.
--
Ron Ramirez
Ferdinand IN
Posts: 1,108
Threads: 89
Joined: Jun 2011
City: Tacoma
State, Province, Country: Washington
You forgot the pic. 
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
I didn't forget...I don't have a good "before" shot of the entire unit right now. 
--
Ron Ramirez
Ferdinand IN
Posts: 1,108
Threads: 89
Joined: Jun 2011
City: Tacoma
State, Province, Country: Washington
OIC. It's just that you indicated there was one. These Pie-in-ears are certainly a PITA to work on, but, IMHO, well worth the effort.
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Most Pioneers (pie-in-ears...I like that  ) are desirable receivers. One like mine is less so, from what I have read, only because of the speaker plugs they used on early 1970s and older models.
I'll post more photos, chiefly that of the audio amplifier board in question, once the parts arrive from Mansfield, Texas.
--
Ron Ramirez
Ferdinand IN
Posts: 1,475
Threads: 69
Joined: Nov 2012
City: Kansas city, MO.
Look forward to your rebuild Ron. Thanks to you and morzh/Mike it is my daily driver in the work room and still playing very well.
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
I did post a "how-to" on AudioKarma showing how to replace the fuse lamps in one of these receivers with LEDs some time back:
http://www.audiokarma.org/forums/showthr...=SX-1500TD
--
Ron Ramirez
Ferdinand IN
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
And Brenda, I did find a frontal shot of my SX-1500TD in my AudioKarma thread:
[Image: http://www.philcoradio.com/images/phorum...e00008.jpg]
This photo was taken before I replaced the meter bulbs, and replaced the indicator bulbs above the dial with LEDs.
--
Ron Ramirez
Ferdinand IN
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
While I wait for parts...
[Image: http://www.philcoradio.com/images/phorum..._00002.jpg]
Here's the audio amp board with the output transistors and heat sink. The two output coupling caps (1000 uF) have both been removed already, and the remaining electrolytics have been desoldered and are waiting to be pulled and replaced with new Nichicons.
--
Ron Ramirez
Ferdinand IN
Posts: 244
Threads: 11
Joined: Oct 2011
City: Black Mountain, NC
Nice to see you still have the original matched output transistors.
Mike
Cossor 3468
GE 417A
Philco 118H
Radiola 17/100
Scott 800B6
Silvertone 6130
Stromberg 535M
Truetone D1952
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
...yes, but not for long...new MJ21194Gs are arriving today...
--
Ron Ramirez
Ferdinand IN
Posts: 15,825
Threads: 554
Joined: Oct 2011
City: Jackson, NJ
Any reason you are changing them, Ron? (unless bad?) Transistors do not go bad from age...for the most part (there is that legendary whiskers growing in Ge).
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Acked. I know. One audio channel is bad. If the original outputs happen to still be good, I'll save the MJ21194G transistors for another project. But if outputs are bad in one channel, I'll replace the whole set.
--
Ron Ramirez
Ferdinand IN
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Well...
I decided to just dive in and replace all of the old electrolytic capacitors...and transistors (including the outputs).
[Image: http://www.philcoradio.com/images/phorum..._00003.jpg]
[Image: http://www.philcoradio.com/images/phorum..._00004.jpg]
This way, this board should be in good shape for another 40 years.
I carefully compared the operating specs of the originals before choosing replacements, since the new transistors do not have the same type of bodies as the old ones (excluding the four output transistors, that is).
--
Ron Ramirez
Ferdinand IN
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Success - I have audio in both channels again! (At least, through headphones...I have no reason to believe that it will be any different with speakers, though.)
[Image: http://www.philcoradio.com/images/phorum..._00005.jpg]
I really should give the same treatment to the power supply board now.
And I now remember that I need to replace the wee little bulb that lights up the dial pointer. That should be fun. 
--
Ron Ramirez
Ferdinand IN
Users browsing this thread: 2 Guest(s)
|
|
Recent Posts
|
|
Philco 16B Parts
|
| The 16B's in the tombstone cabinet sport a 10 1/2" spkr vs the older cathedral sets which uses an 8". The p/p ...Radioroslyn — 12:58 AM |
|
Philco 38-7 Oscillation
|
| I have let this one sit because of other duties. Now I am back, and I have a couple of questions. I hooked up a Hammond ...tludka — 11:16 PM |
|
Philco 38-7 Speaker
|
| I know that when I first started working on this radio, I did not even have a speaker. Once I finally found one it was n...tludka — 11:00 PM |
|
Philco 60 Squealing
|
| I seem to remember eliminating a squeal by changing the IF frequency by a few KHz. Not that you should put too much tru...fenbach — 08:48 PM |
|
Philco 42-390, code 121 speaker
|
| These speakers pop up on eBay regularly, even if at bloated prices.
Honestly, have not seen many parts on swapmeets.morzh — 08:38 PM |
|
Philco 38-7 Speaker
|
| The put-put is not like the speaker problem.morzh — 08:29 PM |
|
Mission Bell Model 19A Car Radio
|
| Hello everyone,
As mentioned in my last post I was going to see if the vibrator / rectifier section could be persuaded...Antipodal — 08:21 PM |
|
Philco 60 Squealing
|
|
Wondering if I did it backwards.
If a coil was wound backwards, the oscillator would not work at all.
Old school...Chas — 07:23 PM |
|
Philco 38-7 Speaker
|
| 4-ohm speaker. Black, Green leads.tludka — 07:00 PM |
|
Philco 42-390, code 121 speaker
|
| #87 on the schematic.
This radio had a 8" Zenith speaker attached to it when I got it. I do don't know the hist...Stevelog — 06:39 PM |
|
Who's Online
|
| There are currently no members online. |
|
 
|
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
