One switch in particular can make your receiver quite def.
This is the attenuator switch on the rear panel. It's easily overlooked, but this dusty att.-switch can make the difference between a receiver, and a piece of useless furniture in your room.
So, if your receiver doesn't quite receive as it used to, JUST CLEAN this little switch on the back-panel with contact-spray.
You don't need to open the receiver, just spray a little bit in from the outside.

Pull the mains-plug before you spray, spray a LITTLE, move the switch a few times and give it 30 minutes to dry. (because you accidentally sprayed on active parts inside of course)

73' Derk
 

Now you can't get the memory function to work wich stores upto 12 channels??

Solution:

The backup batteries are empty (since your receiver could be 20 years old it is a good possibility). At the bottom of the receiver you'll find a small metal plate, witch is fixed by a black knob.
Pull this knob till you feel a click and remove this plate. You will now see a storage-pack for penlight batteries. Refresh those batteries.

But... maybe you are unlucky and there is no storage-pack for batteries at all. This means that the memory-module was never installed, as it is optional... (I'm sorry)
With no optional memory-pcb the FINE-TUNE knob WON'T work either...

To enter a frequency:  Choose the freq. with the tuning-dial
                       Turn the Mch knob to one of the 12 mem presets
                       press  'M'
-stored-
                       To recall press the button right next to 'M'
-the fine-tuning will now operate-

73' Derk PE4CL
 

12 Memories : Managing so few memories is giving you headaches .........

You're facing two solutions :

1. Buying a new one with a 100's cell memory pack or ...
   
    
2. Upgrading your beloved one ! And access to 256 memories.

Summary:

1. Recommendations
   
    
2. Tools required
   
    
3. Parts needed
   
    
4. Mod description
   
    
5. Testing

1. Recommendations

1. This mod is intended to be done only by people who have electronic skills.
   
    
2. The author cannot be held responsible for any damage your manipulations can cause on the receiver.
   
    
3. You're supposed to be familiar with screw-driver and soldering iron, I won't explain how to use this sort of tools.
   
    
4. Never, Never forget to unplug from the main any apparatus you may open. Nowhere in this mod you will be asked to work on a live system.
   
    
5. Check every point during the process, even a simple solder can be defective and can occur the worst.
   
    
6. If something is missing or not easy understandable in this mod application note, please stop and email me. It takes 2 minutes to exchange a mail and 2 days to locate the fault.

2. Tools required

• Philips screw driver
• Soldering iron
• Cutting clamp

3. Parts needed

• Two thumbwheel Switch coding from 0 to F (Hexadecimal) with 1 common and 4 output (2⁰,2¹, 2², 2³) (see following picture for details) (see text for other details)
  
   
• Approx 2 meter of wire small gauge, insulated.
  
   
• A small plastic box which will protect the 2 thumbwheel Switch

Thumbwheel Switch

4. Mod Description

The memory module is a complex circuit therefore we can easily locate the memory chip used to store data of frequency, band, filter.

The (Q) µPD5101LC chip is a memory IC. Its main characteristic are:

• 4 bits data bus, separate in data in and data out (old design)
• 8 bits address bus from AI0 to AI7 called "MEMORY CH SELECT" by Yaesu.

It means this chip has 28 = 256 memory cell and each cell contain 4 bits.
Six '5101' are wired in order to store a word of 24 bits. All of these 24 bits are used to code all the signals generated by the receiver for one particular frequency.
Due to a wish of an inexpensive design of the memory selection, Yaesu designer have chosen a very simple and low cost twelve positions two stages rotary switch (S5) (located on the front of the receiver).
Don't forget that the memory module was an option and a complete (256) selection system may have been a luxurious part if not employed.

The address bus is common for all the memory components and is going outside the memory module by a 13 pins connector (J02) shared with other command.

The pins which interested us is from the pin 4 to 11.

Below is an interconnection diagram on which we can see the wired link between the connector J02 and the two stages rotary switch. The strange wiring of the rotary switch (S5 a and b) is to make a conversion from a hexadecimal coding to a "decimal" incrementation.

The modification consists of removing the 9 wires coming from the module and soldered on the switch. The ninth wire is the +5v. Normally all the lines of the address bus are pull to zero by the resistor net RB01 (see page 3).
The cell address or memory position is set by a switch which put address bus line to logic level "1" (+5v) respecting an hexadecimal structure.

Hexadecimal table :

Cell  AI7   AI6   AI5   AI4   AI3   AI2   AI1   AI0   Value on the switch
1     0     0     0     0     0     0     0     0     0 0
2     0     0     0     0     0     0     0     1     0 1
3     0     0     0     0     0     0     1     0     0 2
4     0     0     0     0     0     0     1     1     0 3

..................
..................

255   1     1     1     1     1     1     1     0     F E
256   1     1     1     1     1     1     1     1     F F

The wiring diagram below is intended to help you to locate each of the 9 wires by its insulator color.

So, cut properly all the wires from the rotary switch.

If those wires are too short to be connected outside the cabinet onto the two thumbwheel Switch, add some new wire to increase the length until it's enough to connect outside.
Don't forget to insulate all the connection point of the wires.

Normally you can manage to extract the wires by the rear side of the receiver.
We will now command the memory position apart from the FRG.

A thumbwheel switch is not an "hard to find parts" especially because it is currently used in computing in order to select the SCSI ID of a HD or scanner for example.

The model required is an hexadecimal one. The mechanical action can be by a rotary wheel or by two push button (+ and -) (those two button will turn the internal wheel step by step). On the rear side you must have 5 connection terminals per switch.
Four of them are used for the output of a 4 bits word and the fifth one is used for the common.
In our application we need to have a 8 bits word (256 possibilities) and its why two thumbwheel switch are needed.
Note : Don't cry if you don't find such switch with 16 positions, you can use two 10 positions switch with binary output, you will only have 100 memories positions. And if you really don't like to manipulate this kind of switch you can easily create your own up/down system articulated on two 74193 , two 7446 and two 7 seg led, you just have to extract the "0v" from the memory module (Pin 1 of J02 for example).

Below is the wiring schematics of the external remote. (Switch seen from the rear side). Note : You are not obliged to respect the hierarchy between the 8 address wires (AI0 to AI7) because you don't mind if the information is not in correct cell inside the memory chip. So you have just to find out the common pin of the switch.

First of all, plug the two switch with the plastic pin . You can add plastic side (left and right) to have a nice finish.
Then drill a hole in the plastic box in which will fit the switch set.
Solder the two common with a short wire.
Solder the +5v wire coming from the module to one side of the common solder.
Solder all of the 8 wires to the 8 switch termination remain left. (don't mind the order).
Close the plastic box.

Check all of what you have done, check all the solder, pay particular attention to the wires coming out from the module, especially if no wire will be hurt by the closing of the cabinet. Put back the top and bottom cover of the receiver.
Switch it on.

5. Testing

Quite easy, just store what you want from the first position 00 to the last FF (256). Then recall all of the 256 memories.
If not : check how you connected all the 9 wires.
Check if you have correctly pointed out the common pin of the two thumbwheel switch.

Tip : if the memory contents does not stay after power off power on, check the battery set accessible from the rear side of the receiver.

Electronically yours, Nicolas