Dynaco FM3 Rebuild Kit with Cap Board, PEC modules, Dial LED & Audio upgrade – $169.00 CAD
This is the full kit including the Cap Board kit, 2X 555001 PEC Modules, 1X 555004 Module, LED Dial Indicator and the parts to complete the audio upgrade.
These are all high quality components ordered from Digi-Key not some sketchy overseas seller. The electrolytic capacitors on the cap board are Nichicon UCS with a rating of 10K hrs. @ 105 and a ripple current rating of 225mA @ 120Hz.
The film capacitors for the audio section are Panasonic ECW-F series. The precision resistors on the PEC Modules are PRP 1% from Parts Connexion. The higher wattage resistors are all Ohmite, Bourns and Vishay. No low quality generic components are used.
Although this is a fairly easy swap this is not a beginners kit. There is high voltage involved, do not attempt this as your first upgrade unless you absolutely know what you are doing.
Assembly
Scroll to the bottom if you would like to download the assembly manual as a PDF.
FM3 Capacitor board assembly and installation:
This board replaces the silver can capacitor, C32 and resistors R36, R37 & R38 which provide the B+ power filtering.
Parts List:
For the 500 Ohm 5 watt you can use the big rectangle ceramic wire wound types or regular wire wound resistors. For the 470R you can use a 1W or 2W wire wound type. You can reuse the original resistors if they do not look burnt and test within spec. Solder all three of the resistors, so they have a small gap between them and the PCB. This allows airflow and prevents the heating and cooling cycles from stressing the solder joints.
Solder R3 first, R1 & R2 second and then all the capacitors. Make extra sure you have the capacitors in the correct orientation, the negatives should all face the same way. If you put one in backwards you are going to have a firecracker when you hit the switch.
Power Supply Original Schematic
FM3 bottom picture
Once the cap board is assembled make sure the FM3 is unplugged and take the cage and bottom off by removing the 4 flat head screws on the sides. Remove the 6V4/EZ80 tube from socket V-9 and put it somewhere safe.
****HIGH VOLTAGE WARNING****
This is not really an absolute beginner project, so I assume you are comfortable working with high voltage and know how to discharge capacitors. If you do not, please pay someone to do this upgrade for you.
Flip the unit upside down so you have the same view as above. Discharge all 4 sections of C32 and unsolder all the wires and resistors attached to it, keeping track of what lug number the wires were attached to.
Lug 1 = Pin 3 of Tube V-9 (6V4)
Lug 3 = Eyelet 22 & 27 of PC-8
Lug 4 = Eyelet 12 of PC-7, 34 of PC-8 & 87 of PC-12
Ground Lug = Lug 3 of the terminal strip & Red/Yellow transformer wire
Now that you have everything unsoldered, twist the metal tabs, so the cap drops out. You may have to wiggle it back and forth a bit from the topside. Once out you can get to installing the new cap board. Undo the small nuts and remove the bolts holding in the V-9 tube socket. Replace the bolts with the standoffs and put the nuts back on. Test fit the cap board on the topside to make sure the standoffs align to the holes in the PCB on either side of the half moon cutout and screw it down with the two screws.
While the PCB is test fitted, run the wires that were attached to the lugs through the hole where the C32 capacitor was and check if they can reach the holes on the cap board. If they are not long enough you can either extend them with some wire and shrink tubing for insulation or just solder on longer wires. Another option is to put in a 4-lug terminal strip and use one lug for each of the connection groups and run short wires to the PCB. If you use a lug strip one of the lugs is usually grounded, make sure you only use that lug for the ground connections.
Once you have all the wires long enough to reach the PCB, unscrew the PCB from the standoffs so you can insert the wires into the holes to be soldered. Solder the wires into the holes as follows:
Pin 3 of Tube V-9 (6V4) to the PCB hole labeled “To 6V4 Pin 3”
Eyelet 22 & 27 of PC-8 to PCB hole labeled “B+ #1”
Eyelet 12 of PC-7, 34 of PC-8 & 87 of PC-12 to PCB hole labeled “B+ #2”
Lug 3 of the terminal strip & Red/Yellow transformer wire to PCB hole labeled “GND”
When all the wires are soldered you can screw the PCB back down to the stand offs and reinsert the 6V4 tube. Double check all your wires are going to the right places and that all your connections are solid before you go for that switch.
Once warmed up you can test the voltages. The voltage on B+ #1 should be around 225V and B+ #2 around 220V.
FM3 PEC Boards Assembly and Installation:
There are two of the 555001 PEC boards and one of the 555004 to be assembled and installed.
Parts List:
555001 PEC BOARD X2
555004 PEC BOARD
For the capacitors you can use 500V Silver Mica or Polystyrene. I have always used the Silver Mica, but they are getting harder to find and more expensive. The resistors are all 1/2W and at least 1% tolerance.
Solder the components into the outlined positions. Do not leave the leads too long as the 555001 boards are quite close together when soldered to the board.
Use some cut component leads or some stiff solid wire to make the leads for the boards. Solder them into holes 1,2 & 3 on each board then bend them 90°. Cut the leads to about 1” for the 555001’s and a bit shorter for the 555004.
Open your FM3 taking off the cage and bottom. You will find the 555004 PEC near the 12AX7 V-7 tube on the long skinny circuit board PC-8
Flip the FM3 upside down and unsolder the 3 leads. You may have to use a solder sucker as the FM3 boards have a lot of solder on them. Be careful with how much pressure you put on the old PEC modules. Do not rock them back and forth when you are taking them out as the traces on these old boards are easy to lift. Use the solder sucker and then a de-soldering wick. The module should drop out without having to pull it. Once the old PEC module comes out just solder in the new one with Pin 1 in Hole 1 etc. If you did lift a trace suck all the solder off it and clear out the hole. When you solder in the new PEC solder that lead last and hold it against the PCB with a flat head screwdriver.
The two 555001 PEC modules are located on the corner of PC-12 circuit board on the corner by the 6BL8 tube V71.
The leads on the 555001’s need to be a bit longer as they need to bend over a bit to prevent the two from touching. Solder them in and bend them so they are not hitting each other. If they are too close and you are worried about them touching, use some Kapton or electrical tape on the back of each. You could also build one board with the components on the opposite side from the silkscreening. It’s no like they move around so I do not worry too much about them.
Other Components:
There are a few other components in the FM3 that should be updated as they degrade over time and affect the performance.
I use Panasonic ECW-F series film caps, but you could use Orange Drop 715P or similar as long as they are film and at least 400V rated. The resistors used for R11 and R13 should be 3W to 5W wire wound and heat resistant.
Capacitors C29 & C31 are located right on the end of circuit board PC-8 near the 555004 PEC module. De-solder them and solder in the new ones. C29 is the .47uF and C31 is the .22uF.
Capacitors C82 & C83 are located on either side of the 12AX7 tube V-72 on circuit board PC-12. Desolder them out and replace them with the two 1uF caps.
Resistors R11 and R13 are located on circuit board PC-8 in front of tubes V-3 and V-4, the 6BA6’s. These resistors are usually burnt as they are running very close to their rated 2W max. De-solder the old ones and when you solder in the new higher wattage ones let them sit about ½” off the PCB to allow them to dissipate heat and not cook the board anymore
The RCA jacks on the back are not the best and do not fit all plugs well. De-solder them and replace them with the ones provided. The right channel positive connects to Eyelet 85 on PC-12 and the left channel positive connects to Eyelet 81. For the negative wire, connect both negatives together using a solid piece of wire and then connect it to the V-72 Eyelet on PC-12.
FM3 Dial LED
This board replaces the dial light bulb on the Dynaco FM3 with a LED.
The kit ships with a clear LED and a 390 Ohm resistor to give off light similar to what the bulb did but uses way less power.
If you want to get fancy and have a different colour LED, use the following chart to choose the resistor required. You do not have to be exact, just do not go way lower as it will exceed the 20ma limit on most 5MM LEDs. The voltage after the diode and resistor is 9V if you want to do your own calculation with your LEDs particulars.
Solder in the diode, resistor, 10uF capacitor and LED as per the silkscreen. For the capacitor you have to bend the leads at 90 degrees so it lays flat on the board. Note the orientation of the LED, diode and the negative side of the capacitor, Ensure you have these correct. The diode has a white line, the cap has a white line and the LED has a little flat edge.
Use the 20-22 gauge solid wire to make leads at the bottom.
If you want to control the brightness, omit the resistor and use a 500-ohm multi turn pot. Bend the legs on the pot 90 degrees so the pot lays flat on the board with the adjuster on the left. Solder the pot in and before you install it, put your multimeter probes on TP1 and TP2 and set the resistance to what you see on the chart above for the colour of the LED you are using. Once installed you can adjust the pot to the brightness you prefer. Do not adjust it too low as you could burn out your LED.
To install the board, you need to unsolder the old light bulb holder. There is generally quite a bit of solder so you may need to use a solder sucker. Once you have the holes cleaned up, put the leads on the board through the holes so the LED lines up with where the bulb used to and solder them. Be careful with height as you want the LED to line up with the hole in the faceplate. Once installed you can bend it around a bit to make it line up perfectly.
De-solder the pads shown
After De-soldering
