Monday, June 18, 2018

Here is a comparison of some of the amplifiers found on eBay.

I have been comparing the specifications of some of the amplifiers that I have worked with:

L-10 Amplifier:
Size: 200x41.5x?? mm
8 Ohm 100 Watts
4 Ohm 200 Watts
2 Ohm 350 Watts +-55VDC
Gain: ?? 
Output Transistors - 3 EA: A1943 C5200

L-15 Amplifier
L-15 Amplifier:
Size: 150x40x?? mm
Size: 5.9x1.57x??"
8 Ohm 150 Watts
4 Ohm 300 Watts
2 Ohm 600 Watts +-55VDC
Gain: 36x
Output Transistors - 3 EA: IRFP240/IRFP9240

L-20 Amplifier
L-20/28 Amplifier:
Size: 110x65mm (L-20)
8 Ohm 200 Watts +-65V
4 Ohm 350 Watts +-60V
2 Ohm
Gain: 34x
Output Transistors - 4 ea D1047 B817
Note: L-20-SE has 2SA1943 2SC5200 transistors
Note: L-28 Includes capacitors and speaker protection

PR-800 Amplifier
PR-800 Amplifier:
Size: 245x65x30mm (or 195x90 with 4 Capacitors)
Size: 9.64x2.55x1.18"
8 Ohm 500 Watts +- 95VDC
4 Ohm 1000 Watts +-90VDC
2 Ohm 1000 Watts +-65VDC
Gain: 40x
Output Transistors - 4 ea TTA1943 TTC5200
Note: Includes Capacitors and Speaker protection
Note there are 2 sizes; one with 2 large filter capacitors and one with 4 large filter capacitors.

NJW0281/NJW0302 Amplifier
NJW0281/NJW0302 450W+450W HIF
Size: 259x73mm
8 Ohm
4 Ohm 450 Watts +-85VDC
2 Ohm
Gain: Very Low - needs preamplifier
Output Transistors - 4 ea NJW0281/NJW0302
Note: ATX power supply pins fit the connectors on the right side.

Wednesday, June 13, 2018

Rebuilding LAB Series LS800 Amplifier with a PR-800 Amplifier

I had rebuilt this LS800 amplifier with a L-15 amplifier but I decided to upgrade to PR-800 amplifiers for much more power.  This is a picture of the old amplifier dissembled.

This is a picture the old power amplifier section.  It was really cobbled.
This is how the PR-800 amplifier boards arrived.  Note that the power output transistors will have to be soldered on.
Pr-800 as it arrives
Here I have added the output power transistors.  I also moved the driver transistors to the top side of the board for mounting on the heat sinks that I have.  Their leads barely reach the tops of their holes.
PR-800 with power transistors
This is what it looks like mounted on the heat sink.  I went back and added washers under the heads of the 3/4 inch 4-40 screws.  Note that little plastic washers must be installed in the two To-220 transistors (Q12 and Q15).  Make sure to check for shorts to the heatsink with a voltmeter!
PR-800 Mounted on heatsink
WARNING!!  Something was really wrong, it tripped the circuit breaker and shorted the output transistors!!!  I eventually found the problem.  The 2SD669 (Center transistor Q13) has to be soldered UPSIDE DOWN on the top board!
Upside Down Transistor on PR800
Here is the schematic of the output section.  Note that the 2SC5200 (Q16, Q17, Q18, Q19) transistors are connected to the + power source and the 2SA1943's (Q20, Q21, Q22, Q23) are connected to the negative power source.  Also not that the two boards are the opposite of each other.  The 2SA1943's will always be next to the power filter capacitors.
The schematic was derived from this schematic found on the internet.  The protection circuits do not match what I received.

Here is a labeled picture

I have both channels working fine now, but only one at a time.

As you can see I cut off one side of the heatsink.  I also switched to silicone insulators because they are less messy.  One channel is missing two power transistors because they were fried when I installed the 2SD669 right side up.

Rebuilding some old speakers

I was given some speakers that I had built back in the 70's and that had been in use at a churhc for about 20 years or more.  They were made to look nice, but I will rebuild them to look tough.  I also want to upgrade them from 25 watts to about 150 watts or more.

This is what I bought to rebuild them with.
This picture compares an old speaker with the new one.
 Initially this is what I had to work with.  I only have one of these bass speakers.
 Here is one cabinet stripped down and the old speakers sitting on top of it.

2018 Chaffee NY Hamfest

I was at the 2018 Chaffee NY Hamfest.  It is a smaller one but I got some great deals. This is what it looked like.
Here is my table.  I failed to get rid of my free stuff!
I bought a metal locator and some speakers.  Here are the speakers that I will use to rebuild my speakers with.

Friday, June 8, 2018

Niles ZR 4630 tear down and rebuild

A friend has a Niles ZR-4630 that he wants made into independent amplifiers.  There are six stereo amplifiers based on the LM3886 IC.  I have been reverse engineering it.  By default the mute is "on" for the amplifier modules.  Here are some pictures of the guts.
This shows the amplifier modules and the power transformer.  We could not get the power on by the on off switch so we hot wired power to the transformer.
This is another view of the transformer and amplifiers.
This is a view of the back side of the guts.
So far I have been able to confirm the pins of the amplifiers. There is more to come.

Wednesday, May 23, 2018

Rebuilding LAB Series LS800 Amplifier with a L-15 Amplifier

I am rebuilding another power amplifier.  This time I chose the L-15 amplifier because it fits in the heatsink.

The L 15 amplifier compared to the old circuit board for size.
 The amplifier totally dissembled into pieces.
 The back panel of the amplifier.
Here is the ebay ad for the replacement amplifier.
The L15 fits nicely in the heat sink
I am using 4 pin power connectors for 5.25 floppy drives for power and ground.
Here is a picture of the old front panel.  I will replaces it with two LM3915's.
 This is the first test.  Power is at + and - 62 VDC.  Lots of gain, I had to turn the volume way down.  Still to go are the input jacks and volume controls.

I have been comparing some of the amplifiers that I have worked with:

L-10 Amplifier:
Size 200x41.5x?? mm
8 Ohm 100 Watts
4 Ohm 200 Watts
2 Ohm 350 Watts +-55VDC
Transistors 3 EA: A1943 C5200

L-15 Amplifier:
Size 150x40x?? mm
Size 5.9x1.57x??"
8 Ohm 150 Watts
4 Ohm 300 Watts
2 Ohm 600 Watts +-55VDC
Gain 36x
Transistors 3 EA: IRFP240/IRFP9240

L-20/28 Amplifier:
Size 110x65mm (L-20)
8 Ohm 200 Watts +-65V
4 Ohm 350 Watts +-60V
2 Ohm
Gain 34x
Transistors 4 ea D1047 B817
Note: L-28 includes capacitors and speaker protection

PR-800 Amplifier:
Size 245x65x30mm (or 195x90 with 4 Capacitors)
Size 9.64x2.55x1.18"
8 Ohm 500 Watts +- 95VDC
4 Ohm 1000 Watts +-90VDC
2 Ohm 1000 Watts +-65VDC
Gain 40x
Transistors 4 ea TTA1943 TTC5200
Note: Includes Capacitors and Speaker protection
Note there are 2 sizes one with 2 capacitors and one with 4 capacitors.

NJW0281/NJW0302 450W+450W HIF
Size 259x73mm
8 Ohm
4 Ohm 450 Watts +-85VDC
2 Ohm
Gain Very Low - needs preamplifier
Transistors 4 ea NJW0281/NJW0302

I think I can fit the PR-800 amplifier version with two filter capacitors so I will try to upgrade to that amplifier instead.  It is coming from China so it will take a while.  Please stay tuned.....

I am rebuilding the VU meters.  I did purchase some LM3915 kits but they only have 10 LED's and I have 12 holes to fill.  I also used round LED's instead of the flat ones that came with the kit. But that version only has 10 LED's.  So I stripped a board from the amplifier bare and installed a LM3915 instead leaving room for more circuitry.
However the rebuilt VU meter was barely visible!  So I had to replace all of the LED's with newer brighter models.  Now to add the two top LED's.  I am planning on using a dual op amp for that job.

Saturday, May 5, 2018

Ford Taurus Passenger Blend Door Actuator

My wife's car had the heat stuck on for the passenger side only.  It was way too hot and it would not turn down.  The problem was a motorized door that was stuck.

Here is an excellent video on how to change the actuator.

I used my fingers to disconnect the electrical connector and that might be easier to do before the actuator is removed.  It is identical to the other connector to the right so you can see what your are feeling for.  Basically you push in a small tab in the center and pull up on the wires.

Here is an great picture of what to look for behind the glove box.


This is how to test the heating and cooling system.
Turn the heating/cooling system off before you start.

The self-test can be initiated after cycling the ignition switch from OFF to ON.
For the self-test, press the OFF and DEFROST buttons together and release them.
Then press the AUTO button - ALL within 2 seconds.
The display will show a moving bar-graph icon for 20 seconds.
If diagnostic codes are present, they will be displayed.
My codes were "12 42" and "22 67"
When done press any button to exit.
Wait 30 seconds to turn the key off for the computer to re-calibrate.

Here is a picture looking into the glove box area.

This picture is going in a little closer.  I moved the white wire harness down out of the way.

Here is the tool setup I used to get to the back screw.  I had to purchase a 1/4 inch universal joint for $5 that you cannot see in the picture.

Here is what is inside of the actuator.  You can test the motor with a 9 volt battery.  The two connections to the motor are on the right side (back) of the motor.  My motor turned a couple of times and stopped.  I thought maybe the mechanics were stopping it, but no it was the motor itself.

Tuesday, April 17, 2018

Audio Centron RMA-1600 Audio Amplifier rebuild

I have been rebuilding aa Audio Centron power amplifier.  The TO-3 transistors were bad and it was cheaper to replace all of the "guts".  The power supply is positive and negative 80 volts.  So I searched eBay for a amplifier board that can handle that voltage.  This is what I found:

1PC NJW0281/NJW0302 450W+450W HIFI Stereo Amplifier Board Assembled AMP Board

Description :

This is completed board.You don't need solder it.
4 Pair MJW0281/MJW0203 for one channel.
so one board has 1 6pcs transistors.
Power supply: DC 45V to 85V
Power: 2X450W (-85V @ 4 Ohms)
PCB size: 259 * 73MM

However if I was to do it over I would use a PR-800 amplifier board.

Here are some picture of the amplifier rebuild.  We used an old heatsink and tapped the necessary holes in it.  The heatsink is upside down while we connect the wires to it.  The power and speaker posts fit the connector pins from an ATX power supply.

Here are some more pictures showing the progress.  We are now testing it at low levels.  The input jacks go through the front volume controls to the amplifier inputs.  The front panel is now powered via a 1K 10 Watt resistor.  The signal inputs to the front panel go through 33K resistors to the speaker outputs.

Its nearing completion with the installation of a speaker protection relay board.  That required that a 12 volt transformer be added next to the main power transformer.

Friday, April 13, 2018

Air Hogs battle Tracker Hacked

I bought an Air Hogs "Battle Tracker" Nerf Missile launcher hoping to put on my Devastator tank.  It is obviously way too big for that!  However I still hope to interface it to an Arduino or Raspberry Pi and add the ability to track targets perhaps by Infrared.

The wired interface appears to be a voltage divider so each button returns a voltage.

Power and ground to the control panel is 3 volts (could be a low battery).  The normal return voltage on the two data lines is 1 volts.  
Pressing the "Fire" button changed PB1 to 2 volts.
Pressing "UP" and "Down" changes PB1 to 1.2 and 1.3 volts
Pressing "Right" and "Left" changes PB2 to 1.2 and 1.3 Volts.

Here is the control circuit board.  I am working on the schematic.

Here is the schematic diagram.  The resistors were measured in circuit so they are off a little bit.  The 32K resistors might be labeled "513" as in 51K.
I rebuilt a solid state relay board to interface to the Nerf missile launcher.  I used this same board years ago to control a phone to light message waiting lights....

However when I tapped into the control board two resistors were destroyed.  R33 and R34 are gone.  I need to come up with a better way to interface to the control board.