uxwbill
Lurking in the Shadows
Someone asked me if I could get pictures of the JC Penney MCS 3050 tuner's internals. The MCS 3050 is your average AM/FM tuner, with the added bonus of a built in Motorola C-QuAM decoder (an MC13020) to play back any AM stereo broadcasts if you can still find any in your part of the world. There are a few on my end, and I'm a big proponent of quality analog AM broadcasting. Done right, AM radio can sound quite good!
My example is still in excellent working condition.
Here come the pictures, along with some explanatory text. Each picture can, generally, be clicked to see a high resolution version. The high resolution pictures are LARGE and those who may be in a limited bandwidth situation or using an older computer are suggested not to view them!
There's the front of the unit with the cover off, ready for examination on my state of the art Electronics Examination Table (sometimes called a "bed"). Note that the front panel is NOT plastic. It's made of metal!
This is the tuning and audio board. It contains a few power components, notably the filter capacitors and a regulation transistor (screwed to the heatsink). Also note that each major functional circuit is outlined and labeled.
And there's the MCU board. The separation is interesting and suggests that someone cared about building a high quality tuner. Somewhere I had the datasheet for that NEC uPD1704C chip, but I can't find it now. It's a 4-bit microcontroller. Note the rather large capacitors, probably used to keep its memory intact when power is not connected to the unit.
These are the numbers printed on the MCU board. I thought it said "TEC", but it clearly does not. This board is identified as PWA-1704 / 72917042-2 .
Here are the numbers from the tuning/audio board:
This board is also marked as "PWA-1704" but the other number has changed: 72917042-1 .
AM tuning is done by a Sanyo LA1247 (intended for and designed with AM stereo capable tuning in mind, and having an improved signal-to-noise ratio as compared to the LA1245).
FM tuning is handled by a Hitachi HA11225 FM IF IC and an NEC uPC1235C stereo detector (for which I could not find a datasheet).
Datecodes on the components all suggest a build in early/mid 1985. On the back there is a datecode of "506", which suggests the sixth month of 1985. (I assume that the code on the back must be given in months, as several ICs have year/week (or week/year) datecodes that would not be possible if the rear datecode were also expressed in weeks.
On the back...mine is serial #4561407, model #683-3050, catalog # 853-6641. Power source is listed as AC 120 V (only, no other taps are present on the transformer, nor is there a voltage selector), for use with 60Hz power. It is said to consume 12 watts while operating.
The UL file number is E55522, listing number 154L, and the product service number--which I assume could have been used to order a service manual back in the day--is 683-3050-00. This was made in Japan.
Speaking of the service manual...might anyone have it? I want to find a copy and would gladly pay for shipping. If need be, I can scan it and return it to you. I do not believe that StereoManuals.com has it, but I have yet to ask and be absolutely certain.
Also: anyone want to tell me how many filters or "gangs" (or their electronic equivalent in this case) this thing appears to have? I'll confess that I don't know about the gangs, and I don't see any obvious filters in the circuit.
Perhaps nobody asked, perhaps nobody cares, but I have a golden screwdriver and an open evening. So...
"Now you know."
My example is still in excellent working condition.
Here come the pictures, along with some explanatory text. Each picture can, generally, be clicked to see a high resolution version. The high resolution pictures are LARGE and those who may be in a limited bandwidth situation or using an older computer are suggested not to view them!
There's the front of the unit with the cover off, ready for examination on my state of the art Electronics Examination Table (sometimes called a "bed"). Note that the front panel is NOT plastic. It's made of metal!
This is the tuning and audio board. It contains a few power components, notably the filter capacitors and a regulation transistor (screwed to the heatsink). Also note that each major functional circuit is outlined and labeled.
And there's the MCU board. The separation is interesting and suggests that someone cared about building a high quality tuner. Somewhere I had the datasheet for that NEC uPD1704C chip, but I can't find it now. It's a 4-bit microcontroller. Note the rather large capacitors, probably used to keep its memory intact when power is not connected to the unit.
These are the numbers printed on the MCU board. I thought it said "TEC", but it clearly does not. This board is identified as PWA-1704 / 72917042-2 .
Here are the numbers from the tuning/audio board:
This board is also marked as "PWA-1704" but the other number has changed: 72917042-1 .
AM tuning is done by a Sanyo LA1247 (intended for and designed with AM stereo capable tuning in mind, and having an improved signal-to-noise ratio as compared to the LA1245).
FM tuning is handled by a Hitachi HA11225 FM IF IC and an NEC uPC1235C stereo detector (for which I could not find a datasheet).
Datecodes on the components all suggest a build in early/mid 1985. On the back there is a datecode of "506", which suggests the sixth month of 1985. (I assume that the code on the back must be given in months, as several ICs have year/week (or week/year) datecodes that would not be possible if the rear datecode were also expressed in weeks.
On the back...mine is serial #4561407, model #683-3050, catalog # 853-6641. Power source is listed as AC 120 V (only, no other taps are present on the transformer, nor is there a voltage selector), for use with 60Hz power. It is said to consume 12 watts while operating.
The UL file number is E55522, listing number 154L, and the product service number--which I assume could have been used to order a service manual back in the day--is 683-3050-00. This was made in Japan.
Speaking of the service manual...might anyone have it? I want to find a copy and would gladly pay for shipping. If need be, I can scan it and return it to you. I do not believe that StereoManuals.com has it, but I have yet to ask and be absolutely certain.
Also: anyone want to tell me how many filters or "gangs" (or their electronic equivalent in this case) this thing appears to have? I'll confess that I don't know about the gangs, and I don't see any obvious filters in the circuit.
Perhaps nobody asked, perhaps nobody cares, but I have a golden screwdriver and an open evening. So...
"Now you know."
My parents are the original owners.
