RadioShack Telephone Tester, Catalog # 43-114

[sjt1803]

Hi
I have one of these on the way that is non operational.
I looked for a schematic for it online. I did find the owners booklet online in an archive.
The owners booklet does include a 1/2 page (tiny) schematic.

The manual has been scanned and changed into a PDF.
The manual itself reproduces fine but the schematic, because of it's size and scanned resolution can not be blown up to a usable size. Component values are distorted.
I'm hoping a member here has this unit and the owners manual and can produce a high resolution scan just of that schematic page.

Thanks
Steve

[paul-f]

Steve,

Are you using Dave Hunter's manual scan from the TCI Library?
  http://www.telephonecollectors.info/index.php/document-repository/doc_details/11647-radio-shack-telephone-tester-owners-manual-model-43-114

Unfortunately the source manual pages are only 5 1/2" x 8" and the printing is quite small with poorly formed letters and numbers, so getting a good scan is problematic.  Printing it on a 8 1/2 x 11 page is twice the original size.

It would be great if someone has a larger source schematic to scan or a clean copy to try and scan at higher resolution and contribute to the TCI Library.

[unbeldi]

The diagram (p.19) is reproduced in ~11x7" format at 300 dpi as a separate image, and it seems to me it should be sufficient to work on the unit.  Granted, some of the component values can be hard to read, but they can also be read directly from the component in the system.

Here is the diagram:

[unbeldi]

BTW, I have looked at this schematic a few times in the past and thought that it would not be terribly difficult to replace the 6805 CPU and PROM with a ~$5 Arduino, which would provide the opportunity to add other functions, like measuring dial speed and break ratio.
The tiny ATmega328 provides a lot more computing power, and signal processing today than the 6502 back then and can probably replace some of the peripheral components needed here.

[sjt1803]

Thanks for the much better looking scan.
I cleaned it up a bit further, it should be usable as it stands.

Thanks for your help


Steve

[sjt1803]

Though not technical, thought anyone interested in this unit might find this interesting.

[sjt1803]

Ok, here's an update, the unit showed up, here are the results of the tests.
As described it was dead. (also missing the holder cap)
Wires from xmfr cut.

I put 5volts on the output of the 5volt regulator and it seems to run.
I tried the cord test and the display worked showing 2 conductor and the pass fail LED illuminated, along with the selection LED above the button.
The other tests are not possible since I'm missing 48volts and the  ring voltages.

The problem is the power transformer is BAD, Marked PT-1950 Co. Transformic Part# 704-0049

I need to find a replacement, or multiples to make up the 3 secondary voltages.

Typically, what would be used for low and high ring voltages?

Someone measured their unit and said the center tapped high voltage winding is 200+v

[poplar1]

The B&K 1045B Telephone Product Tester uses 100 VAC (normal) and 45 VAC (low) @ 20~

RING SOURCE
Frequency:
20 Hz.
Ring Frequency Accuracy
+.I%
Voltage (2 selectable levels):
Low - 45 V rms 25%; Normal - 100 V rms 25%; with lREN
(ringer equivalent number) load.
Ring Sine Wave Purity
Distortion 510%; with IREN load
Off-Hook Detection:
DC line voltage less than 25 volts inhibits ring.
Ring Cycle:
After pushbutton selection of voltage level; approx. 2 seconds on,
4 seconds off.

http://www.telephonecollectors.info/index.php/document-repository/doc_details/12182-b-k-1045b-telephone-product-tester-manual

[poplar1]

Radio Shack Tester supplies 90V and 45V ringing:

SPECIFICATIONS NOTES
Dial Speed
Make/Break Ratio
Loop Test
Receive Test
Transmit Test
Ring Test (Typical)
8 PPS - 11 PPS ± .1275 PPS
58 - 64% :!:: .6%
57 - 600 Ohms DC Resistance
-26 dBm ::+ 5% reference to 600 ohms
-20 dBm ± 5% reference to 600 ohms
Low Ring 45 V RMS
High Ring 90 V RMS
Typical ± 2.3% of Fa
Maximum ± 3.5% of Fa
Supply Voltage
Amplitude for
Detection
Touch Tone Frequency
Detect Bandwidth
Min -19 dBm reference to 600 ohms
Max -2 dBm reference to 600 ohms
Minimum 105 VAC
Typical 120 VAC
Maximum 135 VAC
Note: Above specifications based on 120 VAC only.

http://www.telephonecollectors.info/index.php/document-repository/doc_details/11647-radio-shack-telephone-tester-owners-manual-model-43-114

[sjt1803]

What  kind of current is reasonable for the ring voltages?
Assuming I can find a tapped transformer with a 200+ secondary.

The windings are as follows: all are approx.  12v, 60v, 215, 115(tap) as measured by a collector.

Poplar1, thanks for pointing that info out from the owners ml. I overlooked it, when I was trying to find a usable schematic initially. 

[unbeldi]

What  kind of current is reasonable for the ring voltages?

Very little !   milliamps.

The impedance of a typical C4A ringer and condenser combination is around 8000 ohms at 20 Hz ringing and goes up to about twice that at 30 Hz.  See here, on the forum in this board, for my impedance measurements.  Below is the curve for the C4A ringer in a standard 500-type set.

So, for the sake of illustration let's take an impedance of Z=10 kΩ, at a voltage of E=90 V RMS, you get:
I = E / Z = 90V/10000Ω = 0.009 A.   Nine milliamperes RMS.

[sjt1803]

Update.
I have restored the tester using 3 individual transformers to replace the original.
Total cost for the transformers, $25 (I had a few 12volt transformers) So I only had to get 2
A poor connection on a switching transistor  a rectifier diode and fuse holder the final things..

I found out some more information on this tester. It was built by Gavin electronics in New Jersey.
Gavin was owned by Tandy at the time. They also built antennas for them.
I was told they reverse engineered the B&K tester.
So it was built in the USA.

Steve

[unbeldi]

I was told they reverse engineered the B&K tester.
So it was built in the USA.

Steve

really?  Hmm, perhaps they reverse-engineered it, but they certainly didn't build it that way.

The B&K Precision 1045A doesn't use a microprocessor.  Here is a picture of the internals of mine:

[sjt1803]

My information on how and where it was made came from an engineer who worked at Gavin at the time it was built.
They didn't clone it. But it (the B&K)  apparently was the inspiration for what they came up with.

Steve

[sjt1803]

BTW , thanks for sharing the photo of the B&K , I have never seen one. I like the idea that it was discrete (No LSI or CPU)

Steve