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JD Custom LC2 Eprom conversion board
Fitting into audioline pt345 homebase (039aa)

Hello all. I have this Eprom board and am in the process of fitting it into my rig, but it appears that there are one or two pages missing from the instructions, and i am left with 5 wires and nowhere for them to go... I have figured out most of them and the eprom board is working on both bands (uk/eu) but only on channel 1 all other channels are screwed up.

The green wire on the eprom board is the one i'm stuck on... on the eprom board it goes to pin 3 of the MC145106 chip (osc in), but where on the radio should this wire go? any ideas?

here is the wiring PDF for the eprom and the schematic for the board in the radio.

it goes to pin 3 of the MC145106 chip

Pin 3 is the input for the 10.240 MHz reference frequency. There is presumably a crystal oscillator on the radio PCB that can supply this signal. The PLL won't work without it...

The '106 is an antique PLL that only goes to 3 or 4 MHz, so there must be another downmix oscillator somewhere for it to work, probably in the 15 meg range ((27 meg - 10.695)-15) = the 1 to 3 megs sent to the PLL's other input pin.

Those instructions look old - haven't seen typewriter written instructions in years

Google wasn't much help either:

> Anyone remember JD Custom in Edgware?
> Run by a guy called Joe Delgado - He used to make up a variety of boards for radio conversions.
> Fitting the boards was a doddle - although it took a good few hours to get the radios converted to operate 'cleanly'!

Oh god yes, he'd take a perfectly good working Cobra 148, screw a PA strip on the back, and a freq display on the front, turning it into a semi working dogs breakfast, for the price of a good used FT757.

There were literally hundreds of these "make your rig work better" people in the 80's and 90's, who would gladly add a few extra channels and disable modulation limiters, all for a few dollars, surgery performed between meals on the kitchen table. Did you have the same over there on the UK?

Cheers

Hi thanks for the reply, I'll upload a pic of the eprom board later so you can see it ... its certainly an early board i would say.

The 10.240mhz crystal is removed from the radio and fitted into the eprom board which has the 106 chip and also a cd4070be quad exclusive 'or' gate chip. It would appear that the eprom board has its own oscillator circuit on board.

I seem to remember now i think about it, that Mr Rick from ERC sent me those instructions a few years ago when i took the eprom board out of a scrapper uniden and i do believe that he told me he either designed the board or helped JD Custom to design it (Wish i remembered that yesterday lol).. Unfortunately Rick isn't available for a couple of weeks so i cant ask him about it ATM. Guess i'll wait till Rick is availible


Oh and yea there were loads of KTRD (kitchen table rig doctor) about over here too in the 80's and early 90's lol

EDIT: just re-read your post saying that pin 3 wants a 10.240 signal so maybe i'll try linking it to the 10.240 mhz crystal on the eprom board and see what happens...

The 10.240 signal is needed in 3 places, so maybe it's an OUTPUT back to the main board.

The signal does 3 things:

1) Reference freq for the PLL (where it's divided by 2048 to produce 5 Khz)

2) Second local oscillator on RX (10.695 - 10.240 = 455KHz)

3) Transmit upmixer (VCO upshifted by 455 Khz + 10.240 = 27 MHz)

The 10.240mhz crystal is removed from the radio and fitted into the eprom board

In that case, it's an output back to the RX and TX mixers in the radio.

Remove C59 and C60 from the radio, and connect the signal to the track that joins these 2 caps together.
This in turn will connect to R97 (TX mixer) and C12 (RX 2nd mixer).

Without that signal, the RX and TX performance is going to be severely limited

Cheers

You are 100% correct in what you say.. the 10.240Mhz crystal is connected to pins 3 and 4 of the MC145106 on the eprom board, there is a yellow wire from pin 4 on the MC145106 that connects to C60 on the uniden board and on to where it needs to. And so the green wire is still homeless

Without the green wire (that is connected to pin 3 on the MC145106) connected to anything the radio is working correctly on channel 1 of both bands. 5 watts RF output power, on correct frequency and good audio. on any other than channel 1 the power drops right back to barely nothing and the frequency drops to 26.880 Mhz.

This eprom board can be used with TC9119 PLL's and also LC7137 PLL's so i'm wondering, maybe the green wire is not used in the Uniden radios with the TC9119 PLL.

Initially I thought that I may have soldered the ribbon wires to the PLL/channel selector back to front, so I reversed them with no difference.

And so the green wire is still homeless

Cut it off, it must be for another application (radio). If the set receives and transmits OK on channel 1, the 10.240 signal is reaching the 3 places it needs to go.

on any other than channel 1 the power drops right back to barely nothing and the frequency drops to 26.880

It's "out of lock" and the 26.880 is probably just the low freq limit of a free running (unlocked) VCO. Confirm this be measuring the DC voltage at TP1 (or R52, a 10K resistor). If it's under 0.5V, the PLL is unlocked. Double-confirm this by measuring the voltage when it's on channel 1 - it should have over 1V on it (this will change slightly on TX due to the 455Khz VCO shift).

If that's OK, check for the reason. " Out of lock" can be caused by losing the 5V rail to the PLL (usually as a result of a programming line shorted to ground) or by incorrect programming. The possibility that the EPROM has lost it's memory is unlikely, but cannot be overlooked.

Without a circuit diagram of the mod board, I can't give you a "check the voltage on pin X" instruction.
Do 3 things:

- what is the number of the PLL and EPROM on the mod board? The part numbers will start with "MC and "27" respectively, given the age of the board.

- what other "major" parts such as ICs are on the board, and how do they connect to the EPROM / PLL?

- Do a list of the pin voltages of the ICs on channels 1, 2, 3, 4, 5, 20, and 40.

I then should be able to point you in the right direction.

Have fun...

This should help... I spent all afternoon drawing it and it may contain errors, but should give you a reasonable idea how this eprom conversion board works:



I'll check for voltage at TP1 tomorrow. I believe you could be right that its 'going out of lock' thats what it 'feels' like.
It is possible that the Eprom board may be corrupted... its been floating around waiting for me to re-fit it for over a year, and it was not stored in anti-static bag

Also check the connection to pin 6 of the PLL - it selects the divide ratio (1024 or 2048). I can't see the need for this, as it would have to be set for 2048 to allow the thing to transmit.
((10240 / 2048) * 91) = 455 Khz, which is the TX/RX shift. SSB sets don't need the offset but would need a clarifier circuit... which is not present.

The 15 Mhz signal I mentioned earlier is generated by a frequency tripler (the 68p cap and the bottom BC549), so you won't find that crystal there.
The 10.24Mhz is divided by 2 and appears at pin 5. (10.24/2)*3 = 15.360 Mhz. This is used to downmix the PLL to something the old PLL can handle OK.
If channel 1 is working, the tripler must be OK.

If you can't work out the fault, let us know the PLL and EPROM pin voltages on the channels nentioned earlier.

Cheers

Ok it looks like the eprom may be bad. Here are some voltages:

TC9119p PLL in uniden radio:

Pins 10 to 18:
7 7 7 7 7 7 7 7 0 Ch 1
7 0 0 0 0 7 7 7 0 Ch 2
7 0 0 7 0 7 7 7 0 Ch 3
0 7 0 7 7 7 7 7 0 Ch 4
0 0 0 7 0 7 7 7 0 Ch 5
0 0 7 0 0 7 0 7 0 Ch 20
0 0 7 0 0 0 7 0 0 Ch 40

with ribbon cable to eprom board connected, pins 10 and 17 drop to about 4.5v


MC145106 PLL on eprom board:

Pins 10 to 18:
0 0 4 4 0 4 0 4 0 Ch 1
0 0 0 0 0 0 0 0 0 Ch 2
0 0 0 0 0 0 0 0 0 Ch 3
0 0 0 0 0 0 0 0 0 Ch 4
0 0 0 0 0 0 0 0 0 Ch 5
0 0 0 0 0 0 0 0 0 Ch 20
0 0 0 0 0 0 0 0 0 Ch 40

So the eprom is getting correct signals from channel selector/TC9119 PLL and on any other than channel 1, it would appear that the eprom is not sending the right signals to the MC145106 PLL chip.

Voltages on pins 3 to 10 (the address lines) are needed - you could have a wiring mistake here and be calling up unprogrammed area inside the EPROM.

Does the voltage at pin 6 change between ch. 40 and any other channel? It should stay the same.

Also, I can safely assume you do not have a EPROM programmer? A hex dump of the contents would make it a lot easier to see what input was supposed to go where...

pins 10 through 18 on the TC9119 goto pins 3 through 10 on the eprom, although now i notice that pin 10 and pin 18 go through the or gate chip so i will double check those.

I do not have a Eprom programmer, but i do have a homebrew eprom reader circuit that plugs into a PC serial port, that i use to recover lost supervisor passwords on IBM laptops... Maybe i could use this to read the Eprom on the board. The eprom reader has 3 wires which goto SDA, SCL and Ground... guess i'll look for a datasheet for the eprom to see if it has the required pins.

Don't know if this is of any use to you Norm, this is for the ISS3 LC1 board Dave.

Thanks Dave i'll Check those against my eprom board to see if its getting the correct inputs. (assuming that / is high and blank is low).

if the eprom is getting the correct inputs but incorrect outputs, can i assume that the eprom is bad?

Yes Norm,
High is / and blank is low. Don't forget they are different boards, mine is the ISS3 and uses a 2732 EPROM not the 2764,
having said that the switch codes to the EPROM input pins should be the same, they can't change.
I can offer to read your EPROM for you so you'll have the program that's in it.
The chart above is what Rick sent me some time ago and there are different versions of the conversion as Rick will tel you.
Dave.

Rick sent me the wiring info for my eprom board ages ago when i took it out of a scrap radio, but unfortunately he's away at the moment so i cant ask him about it.
I'll be testing the eprom input voltages tomorrow... i'm pretty sure they will be ok, as i double checked that the radio was working perfectly before fitting the eprom.

I did look today for a PLL truth chart for the President Jackson which uses the MC145106 PLL, my thinking is that on midband the program pins on the MC145106 on the eprom board (output from the eprom) should be the same as the Jackson... however my search was fruitless

The eprom reader has 3 wires which goto SDA, SCL and Ground

That's an EEPROM reader, not an EPROM - that extra E at the start indicates a completely different component.

An EEPROM is "serial" - only 2 wires are needed for date transfer (SDA and SCL).
An EPROM is parallel a 64KB device would need 24 wires for data transfer.

EPROM is faster (all bits are transferred simultaneously) but needs a lot more trackwork on the board.
EEPROM is slower (but still perfectly adequate for most uses) but needs just 4 connections - power, ground, data (SDA), and clock(SCL).

They are both non-volatile memory devices but the interface is very different.
If you are familiar with modern computers, its like comparing PATA(IDE) and SATA hard drives.
Both store your data, but the connection to the motherboard is completely different.

EEPROM really needs a micro to do the data transfers, that's why one of these is not used on your board.
We use EEPROM and an ARM microprocessor on our Digiswitch boards, haven't used an EPROM for a few years now.

if the eprom is getting the correct inputs but incorrect outputs, can i assume that the eprom is bad?

Assuming you have the addresses (inputs) connected correctly, yes.

As Dave nicely to read the EPROM for you, post the contents as a hex dump here, and we should be able to work out from there where things have gone wrong.

Cheers

Norm,
Don't bother looking for a truth chart for any other radio that uses the 145106 PLL, it won't help you, It'll just make matters worse.
The channel switch codes used for the TC 9??? PLL's are not in any specific order that makes sense, as you can see in the list above, there all over the place.
I'll try to load another chart I have to see if that's any better. The chart below is the original channel switch codes using the standard factory fitted PLL.

All the eprom inputs from the TC9119 to the eprom test fine, so I tested the output pins and they were mostly wrong.

I have took the eprom board out of the radio, and happened to be chatting to a retired radio doc (in tesco's lol) who took the eprom board home to test it. His report is: "4 of the programmable output pins of the eprom are dead"

So I've now put my audioline back to standard 40ch and will leave it like that (unless I happen find a cheap board or TC9106 chip off ebay to piggyback sometime)... I hardly ever use the audioline so its not a problem.

Thanks for all your help folks!

Norm,
You could have sent it to me and I would have programmed you another one, as long as the original program is stil on it.
Dave.

i'm not sure if you could read the program with 4 dead legs on the eprom... I'll freely send it to you if you fancy having a play with it, but its not worth me spending much money on. PM me your address

The channel switch codes used for the TC 9??? PLL's are not in any specific order that makes sense, as you can see in the list above, there all over the place.

It's done that way to save cost - the address lines of the PLLs ROM are connected to the LED channel readout pins of the channel switch. This saves a penny or two as seperate switch lines for the PLL and channel readout are no longer needed.

i'm not sure if you could read the program with 4 dead legs on the eprom

No, you wouldn't be able to. However, 4 dead data lines is extremely unlikely, another fault on the board or a wiring mistake will make it look like the EPROM is at fault.
Pull it out and 95% of the time they read good in a standalone reader.

Another thing to do is do away with the EPROM altogether and connect the PLL to a PC.
You'll have scanning, searching, 26-29 Mhz (if the VCO and mixers can handle the bandwidth), a spectrum display, and a channel activity log.
The WINScanner software is free from http://malzev.tripod.com/radiodoc/software.htm along with details on how to connect the PC to the radio.
You might have to ask him kindly for a UK version though and supply him with a "truth chart" showing what pins control what frequency...

Have fun

I have the eprom out and ready to send to Dave when the post office opens.. then we will know whats going on with it and weather it will read or not. I'm pretty sure the eprom is corrupted, but it may not be...

Using the channel display lines to run the PLL switching is a great idea, although annoying if you are trying to figure out the truth chart

Connecting the radio to the computer sounds like fun I have an old major M588 in the shed maybe i'll have a play with that and my old laptop... (i was planning to modify the 588, by removing the channel selector and fitting 6 individual switches to allow manual binary programming for channel selection.. i saw it mentioned on a forum somewhere that it could be done and it sounded fun... thankfully the PLL02A truth chart is simple binary)

I have an old major M588 in the shed

There is a PLL02A version of the scanner app - hook that up and you'll have more channels than you would now what to do with

Thanks to Dave (Zodiac), here is a dump of the eprom:
In .hex format http://normsweb.com/ext/eprom.hex
In .txt format http://normsweb.com/ext/eprom.txt

It seems like it may be corrupted as the data makes no sense (not that I know a lot about hex programming), and looks totally completely different to the V3 eprom data

"4 of the programmable output pins of the eprom are dead"

They are all OK, all 8 lines working are needed to show the numbers you have in the hex dump.

However, it looks like data line D4 (the least sig bit of the tens digit) is in trouble - nearly (but not all) of the combinations are high.
This indicates a partially erased device - erasing then with UV light sets all the bits high, not low.

Obtaining the correct data and reprograming it should get the board going again.

If you can't get the correct data (i.e. by copying it from an identical working board) you would have to code it from scratch - not really viable other than as a learning exercise.
If you decide to go down that path, you'll need an EPROM programmer and a UV eraser. A couple of hex thumbwheel switches (to figure out the N-Codes) will make this job a bit easier.

Enjoy...

Thanks for that explanation, I dont think i'll be able to work out the programming myself... (sounds like it will be a lots of maths involved lol)

I'll see if i can find anyone who has a dump from a working one, or if i can find a working one somewhere, although i don't hold out much hope of that

Where's the fun in that?

sounds like it will be a lots of maths involved

Hex 101:

Numbers in computers (and radios!) are represented by voltages on wires - these can either be off (low) or on (high).
By putting different voltages on different wires, we can "change" things (such as our operating frequency).

It's a bit hard to read if written down as highs and lows (what is HHLHHLLHHHHLLLHH?)

To make things a bit easier to read, we use HEX. This groups them into sets of 4 wires, each one called a HEX DIGIT.
Because there are 16 combinations of highs and lows for each digit, the digits 0 to 9 are not enough, so A, B, C, D, E, and F are added.

LLLL = 0
LLLH = 1
LLHL = 2
LLHH = 3
LHLL = 4
LHLH = 5
LHHL = 6
LHHH = 7
HLLL = 8
HLLH = 9
HLHL = A
HLHH = B
HHLL = C
HHLH = D
HHHL = E
HHHH = F

The first letter has a "weighting" of 8 if high.
The second letter has a "weighting" of 4 f high.
The third letter has a "weighting" of 2 if high.
The last letter has a "weighting" of 1 if high.

Therefore, LHLH is equal to 0 + 4 + 0 + 1, in other words, 5.

Your EPROM has 12 addresses (inputs) and 8 data lines (outputs).

We need one hex letter for each 4 wires, so you need 3 digits for the address and 2 digits for the data.
So, if address 201 is programmed to give out a data value of 7F, this means that:
Putting the input lines to LLHL LLLL LLLH will cause the output lines to change to LHHH HHHH.

Get it?



Here's a typical "hex switch". Note that there are 5 pins: the common supply (C) and the 4 outputs marked 1, 2, 4, and 8.
Put 5 volts onto "C"and select position "5". #8 will be 0V, #4 will be 5V, #2 will be 0V, and #1 will be 5V.

Complicated maths? Not really, if you have 2 switches like the one above. Connect them to the PLL and make a chart as to what code gives what frequency.
Use a multimeter to see what the addresses are. Program EPROM and enjoy your radio...

Hope this helps - let us know if you didn't understand any bits it.

Cheers

Thanks once again for an interesting and detailed reply.

I understand about working out what code is required to get the output PLL to change frequencies, but I don't understand how to convert the code coming in to the code thats needed coming out.

so if the input for ch1 would be HLLLLHHH and the output needs to be LHLLLHHH for example, how do you tell the eprom to convert it? and it would be different for each channel, thats what i dont get

ps. (what is HHLHHLLHHHHLLLHH?) its D9E3

Here's the pinout of the EPROM:


The address lines are the inputs to the EPROM.
The first digit (thousands) is A12. This can only be high (1) or low (0).
The next digit (hundreds) is A8, A9, A10, and A11, so this can be 0 through to F.
The next digit (tens) is A4, A5, A6, and A7, so this can be 0 through to F.
The next digit (units) is A3, A2, A1, and A0, so this can be 0 through to F.
Therefore, the INPUT or addresses range is from 0000 to 1FFF.

The data lines are the outputs from the EPROM.
The first digit (tens) is D4, D5, D6, and D7, so this can be 0 through to F.
The last digit (units) is D3, D2, D1, and D0, so this can be 0 through to F.
Therefore, the OUTPUT or data range is from 00 to FF.

The other pins are used for programming and for multi-EPROM circuits, ignore these. Connect them to ground, except for NC pins which are left unconnected.

It's easier to understand if you ignore pinout and unused lines in the schematic:


If the PLL wanted 6F for FCC channel 1 RX and AE for TX (more on how to do this further on) then the EPROM DATA has to be 6F and AE.

Put your radio to FCC mode and the channel selector on channel 1. Measure the voltages on the channel selector pins that go to the addresses.

If it is, for example, 002A on receive, this will be 102A on transmit (because the 5V TX line goes to A12 in the above circuit, adding +1000).

With the EPROM programmer, program 6F into address 002A and AE into address 102A.
Repeat the measurements and programming for all other channels.

Result: when the FCC mode is selected and the selector is turned to channel 1, the EPROM gives out 6F and the radio receives on that channel!

There are 2 ways of working out the DATA codes needed.

Method 1: use a couple of hex thumbwheels:


Set the thumbwheels to the halfway mark (80), Radio should lock OK. Write down frequency.
Set it to 81 and measure again. It should have moved by 5 or 10 Khz. This is your step.
You can now make a chart from 00 to FF showing all 256 combinations, by simple derivation.
For example, if 80 gave 27.305 and 81 gave 27.315, it follows that 82 must be 27.325 and 83 gives 27.335, and so on.

Method 2: use good old mathematics You'll need to know the downmix and reference frequencies before you can do this.
Example: Radio uses 10Khz reference and a 15.360 downmix. Calculate code for FCC channel 40 RX (27.405 Mhz):

VCO = RF - IF, so VCO = 27.405-10.695 which is 16.71 Mhz.
Fin = VCO - Downmix, so Fin = 16.71 - 15.36 = 1.35 Mhz.
The next step requires Khz, not Mhz, so multiply by 1000 to get Khz: 1.35 x 1000 = a value of 1350 Khz for Fin.
NCode = Fin / Ref. 1350 divided by 10 = 135.

135 is the decimal value, NOT the hex value our EPROM programmer wants.
Use the Windows calculator accessory (change it from Standard to Scientific view) to convert:
135 decimal = 87 hex. Therefore we program 87 into the EPROM to hit 27.405 at the address combination we wand to make the radio go to 27.405.

You can now make a chart from 00 to FF showing all 256 combinations, by simple derivation.
For example, 86 should give 27.395 and 85 should give 27.385, and so on.


Because the reference and downmix cannot be easily determined in many cases, I prefer method 1.
I keep a pair of thumbwheels soldered to the data pins of a 28 pin EPROM socket to do this. Total cost was under $20.

Hope I explained it clearly enough

Cheers

Ah, ok! I think my tiny brain get it now lol!

The inputs from the channel selector to eprom are address and the output to the PLL are data, so that when the input address is xxxxxxxx the output data is set to xxxxxxxx

So, getting the address data should be easy, by using a PLL truth chart for the TC9119 PLL chip (or testing it with voltmeter a you suggest).
The output data in theory could be found by using a truth chart for the MC145106 PLL chip... as for EU band the standard 1-40 of the MC145106 would be required.
But then i would have to work out how to get it to do the UK frequencies

it would be a lot easier to buy a new eprom board

The output data in theory could be found by using a truth chart for the MC145106 PLL chip

No, as this can change for different radio designs.

Old school PLLs like the MC145106 were not fast enough to directly control the VCO frequency, so downmixing had to be used so that the thing could work.
The MC145106 tops out at 4 Mhz, and our 27 meg radio needs much higher.
Most 27 meg radios use an IF of 10.695 Mhz, which needs an oscillator of 27 megs - 10.695 (for RX, to keep it simple, TX is a bit different)
To receive FCC channel 40 you need a 16.71 Mhz oscillator (27.405 - 10.695).

16.71 is more than the 4 Mhz the MC145106 can handle, see a problem?

A downmixer is used (the EPROM board uses 15.360) to overcome this.
The 3 transistors and the associated components are the downmixer.
The 10.24 is halved then tripled which gives 15.360 Mhz. This is then downmixed with 16.71 to give 1.35 Mhz which our PLL can handle.
Note that the PLL never "sees" the 16.71 Mhz directly.
Therefore, there can be no standard "truth chart for the MC145106 PLL chip".

it would be a lot easier to buy a new eprom board

But a lot more educational to learn how to do it yourself

I''d be buying a couple of hex switches and wiring them to the data lines and working out the codes for myself...

Cheers

Cheap hex switches in the UK:
http://www.ebay.co.uk/itm/HEX-RED-KNOB- ... 19c17d7bac

Mount them on some perf board and wire them to the (with the EPROM now removed) EPROMs data connections.
Or, if the EPROM was mounted in a 28 pin socket, wire the switches directly to a new socket. This can then be plugged into the existing socket.

You''ll need to add a few resistors and a capacitor, that's easy enough though.

You'll have the data coding worked out, and know how capable the radio is (i.e. it's usable bandwidth) in no time.

If you do that, I'll show you how to write a new hex file that you can send to Dave and have him program a new EPROM for you.

You will then know exactly how this stuff works and know how to fix it if something doesn't operate as expected.

Enjoy...

it sounds like a do-able project, though i have a few other projects on the go first so it this will have to wait till i can clear some space on my workbench...

I did look at those hex switches this morning funny enough and nearly bought them then... I have plenty of vero board here so could make up a hex switch circuit easily. I know that the common of each hex switch will need to be fed with about 5v so it can pull the PLL high when on or low when off, where do the resistors and capacitor come into it?

I did also have a quick look last night about making a homebrew eprom programmer that plugs into computer, but as i'll only probably be doing one eprom with it, it may not be worth it.

where do the resistors and capacitor come into it?

It depends on the switch design - there are 2 types of hex switch.

I only showed the least common type before as it's easier to understand.
These have the common connected to +5V and the outputs are used directly.

There is one problem with that approach - what happens if one of the switch outputs is shorted to ground (faulty component, wiring mistake, solder splash, etc)?
Hopefully the supply limits the current, or things are going to get hot (melted switches and wiring, anyone?).

Most hex switches are inverted - so a pullup resistor to +5V (typically 10K) for each output is used. The common of the switch connects to ground.
This "pulls up" the output to 5V when it's open, and forces it to 0V when it's closed.
Switch position 0 = all closed, which gives LLLL.
Switch position F = all open, which gives HHHH.

So the end result is exactly the same, but if there is a short to ground, current is limited to half a milliamp (5V / 10,000 ohms).
The circuit still won't operate correctly, but no permanent damage occurs.

The listing didn't say what type of hex switch it was, so the placement of the resistors would have to be shown after you buy the switch and do a multimeter measurement on them.
Either type will work for you, they are just wired up a slightly different way.

The capacitor is a simple common to supply bypass, to remove any residual hum, RF, etc. If there is another nearby bypass cap, you can probably get away without this component.

Cheers

I found some mini hex switches like this:


so i built this little circuit:


The mini hex switches are not inverted, so i have added a 10k resistor to each output pin.

If i build another one i would probably use coloured ribbon cable rather than the grey, but hey-ho, it should do the job ok... now i just gotta clear some jobs off my bench so i can get the radio back on there...

First of all, make sure they are not inverted - when the switches are at position "0", there should be NO connection between any of the pins (assuming they are 5 pin switches).
If they have more than 5 pins, there should be NO connection between any of the output pins at position "0".

Repeat the above at position "F", all of the pins should now be joined.

When you are 100% sure the above is correct, here's where the resistors and capacitor go:



You should now be able to derive the radio's hex codes.
Bear in mind that the codes will be different for RX and TX.

Make sure that FS (pin 6 of the MC145106) is at 0V (this should give 5K steps).

Make sure that P8 (pin 9 of the MC145106) is at 5V initially.
Making this 0V will drop the radio by 1.28 Mhz.

Have fun...

First of all, make sure they are not inverted - when the switches are at position "0", there should be NO connection between any of the pins (assuming they are 5 pin switches).

Yes they are 5 pin switches and they are not inverted as i said in my last post. I tested the switches at 00, FF and 55 when i got them as they were not listed as hex switches, but as alpha-numeric switches so i tested them to make sure they were actually hex switches.

wiring in the manner you show, is how i would have wired the switches (but with + and - reversed) if the switches were inverted. I thought the resistors were there to protect the 5v supply if one of the output pins was accidentally grounded, thats why i wired a resistor in series with each output pin... in the diagram above there is no protection if one of the output pins is shorted (unless i'm missing something)

That's correct, and why inverted (common to ground) switches are used on most real-world applications.
If you want to play safe, put a low value resistor (say 68 ohms) in the 5V line that feeds both switches, this will limit the current to a safe value (about 75mA) in the event of a short.

Cheers

Wow i cant believe a month has gone by and i haven't got round to actually wiring the Hex Switches into the radio yet... Unfortunately this Audioline homebase has to take a back seat, as more important stuff has to be done first. (i have at least re-wired the hex switches, so they are correct now!)

Hopefully, I'll be able to get to it soon (don't hold your breath )