Hi Guys, I am trying to find info on the eprom conversion thats in my MK1 Ham Jumbo.
The only identifier I can find on the eprom board is the number 88081 (or it could be 88031), Anyone Know anything about this eprom board?
My radio has this eprom to give UK 40, but then it seems to have a seperate 10kc shift mod and seperate LoLo mod???
I'm wondering why the eprom wasn't used to do everything...
I'm also gonna post this on ricks forum for maximum coverage
88081 Eprom conversion board - any info?
Re: 88081 Eprom conversion board - any info?
Norm,
With old radios like yours that have been around for some time, you'll find they have been to many rig doc's over the years, each one having done a different conversion for each of it's owners.
I'd have banded it with an Eprom and used two crystals, one just to give the offset for the UK band to save having to keep retuning every time you go on the UK band and one for all the FCC bands.
But that's my way of doing it.
Dave.
P.S. Have you got an Eprom programmer to read what's on it ?.
With old radios like yours that have been around for some time, you'll find they have been to many rig doc's over the years, each one having done a different conversion for each of it's owners.
I'd have banded it with an Eprom and used two crystals, one just to give the offset for the UK band to save having to keep retuning every time you go on the UK band and one for all the FCC bands.
But that's my way of doing it.
Dave.
P.S. Have you got an Eprom programmer to read what's on it ?.
How far is it.
Twice it's length from halfway.
Twice it's length from halfway.
Re: 88081 Eprom conversion board - any info?
Hi Dave,
No i do not have an eprom programmer... however i do have a home made eprom reader which i use to find passwords on locked out laptops, maybe i could use that to read this eprom (if I knew which pins were SDA and SCL).
The eprom itself seems to do the UK offset in this mod. its got a UK81/FCC switch which puts it on uk band with no retuning or anything.
The guy i got the radio off said that it had something done to it and if you add more switches the radio will do more things... i'm guessing that he was talking about the eprom board, so it would be good to know some info about the board to find out if the eprom can do more than just the uk band which it is doing now.
No i do not have an eprom programmer... however i do have a home made eprom reader which i use to find passwords on locked out laptops, maybe i could use that to read this eprom (if I knew which pins were SDA and SCL).
The eprom itself seems to do the UK offset in this mod. its got a UK81/FCC switch which puts it on uk band with no retuning or anything.
The guy i got the radio off said that it had something done to it and if you add more switches the radio will do more things... i'm guessing that he was talking about the eprom board, so it would be good to know some info about the board to find out if the eprom can do more than just the uk band which it is doing now.
Norm
Re: 88081 Eprom conversion board - any info?
Hi Norm,
The smallest Eprom I use is the 2716, it has enough room to give you 32 bands. How many do you need ?.
Dave.
The smallest Eprom I use is the 2716, it has enough room to give you 32 bands. How many do you need ?.
Dave.
How far is it.
Twice it's length from halfway.
Twice it's length from halfway.
Re: 88081 Eprom conversion board - any info?
Yea, I reckon 32 bands ought to be just about enough Dave! 
Although some how i dont think the Jumbo can handle that many 
Although some how i dont think the Jumbo can handle that many Norm
Re: 88081 Eprom conversion board - any info?
Well you could use a 2732, that has the capability of 64 bands or a 2764 with 128 bands, is that enough for your Jumbo ?.
I have an Eprom that'll do 25.615 to 27.855 and the UK's that's 6 bands but you have to extend the VCO, not an easy job, it requires a very small 12v drill and a lot of patience.
You'd also need to alter the band switch to a 6 position switch, another skill you have to learn, but it's well worth the effort and looks better with them all on the one rotary band switch instead of flicking loads of different switches.
Food for thought Norm, that's got your taste buds going now.
Dave.
I have an Eprom that'll do 25.615 to 27.855 and the UK's that's 6 bands but you have to extend the VCO, not an easy job, it requires a very small 12v drill and a lot of patience.
You'd also need to alter the band switch to a 6 position switch, another skill you have to learn, but it's well worth the effort and looks better with them all on the one rotary band switch instead of flicking loads of different switches.
Food for thought Norm, that's got your taste buds going now.
Dave.
How far is it.
Twice it's length from halfway.
Twice it's length from halfway.
Re: 88081 Eprom conversion board - any info?
Dave, you read my mind! How did you know I'm planning to fit a 5 position rotary switch to the Jumbo. Its just a matter of finding a suitable switch for the job. Fitting the switch won't be a problem as I'm good at things like that.
Here is a Pic of the Mods in the Jumbo:
I'm not 100% sure but i think that the "Audio Mod?" is actually a standard part of the jumbo. Notice how the 10Kc shift mod has been built on to the legs of the chip and is just left floating... Never heard of vero-board then? 
The "unknown" mod is about 1cm square and has a couple of diodes and a couple of capacitors on it and connects to pin1 of IC2 and ground. I'm not sure where the orange wire goes.
All of these mods work ok, but man they look messy and that irritates the hell outta me
Here is a Pic of the Mods in the Jumbo:
- Jumbo_Mods.jpg (128.9 KiB) Viewed 19994 times
The "unknown" mod is about 1cm square and has a couple of diodes and a couple of capacitors on it and connects to pin1 of IC2 and ground. I'm not sure where the orange wire goes.
All of these mods work ok, but man they look messy and that irritates the hell outta me
Norm
Re: 88081 Eprom conversion board - any info?
Norm,
That Eprom board looks very very much like one of mine but the audio mod is not, if it is one of my Eproms it'll have DZ63 on it somewhere.
A closer photo of each mod might be better as that one looks like what I do with the web cam, crap to say the least.
Be very careful when altering the band switch you can't afford to damage the switch as the Jumbo has longer shafts than any other radio. If you do damage it beyond repair it's not the end of the world. You can fit a shorter shafted switch from another radio but you have to cut the front from a scrap radio with a suitable hole and bend it to fit the Jumbo, so it's brought further foreword so the end of the shaft fits flush with the other controls, then solder it in place.
I've just finished doing one and had to fit 7 new rotary controls because of some radio Ham cutting the knobs in half to fit the shorter shafted controls he'd glued on.
Dave.
That Eprom board looks very very much like one of mine but the audio mod is not, if it is one of my Eproms it'll have DZ63 on it somewhere.
A closer photo of each mod might be better as that one looks like what I do with the web cam, crap to say the least.
Be very careful when altering the band switch you can't afford to damage the switch as the Jumbo has longer shafts than any other radio. If you do damage it beyond repair it's not the end of the world. You can fit a shorter shafted switch from another radio but you have to cut the front from a scrap radio with a suitable hole and bend it to fit the Jumbo, so it's brought further foreword so the end of the shaft fits flush with the other controls, then solder it in place.
I've just finished doing one and had to fit 7 new rotary controls because of some radio Ham cutting the knobs in half to fit the shorter shafted controls he'd glued on.
Dave.
How far is it.
Twice it's length from halfway.
Twice it's length from halfway.
Re: 88081 Eprom conversion board - any info?
I always have problems with my digital camera taking good shots of circuit boards (even with the "macro" setting)... I'll try to get a good pic of each mod individually, but dont know how well it will turn out.
As for the switch, i hadn't planned on modifying the original, i had thought to get one from an old superstar or something - but now i learn that the shaft will be too short, i must get another idea. maybe some form of shaft extention. perhaps a tongue and groove with the shaft from another pot glued on to make the length...
How could anyone cut radio knobs in half to make them fit the radio, what a butcher!
I'll look tomorrow to see if i can see your ident anywhere on the eprom board
UPDATE: Here are better(?) pictures of the eprom board.
The actual eprom used is: Hitachi HN462732G and has 02A written in pencil on the white sticker on the top
UPDATE 2 I have been looking into why the wires from the tune switch have been removed. When the radio is put in UK mode, the eprom is switched and also a resistor is switched in across the tune pot to give the UK offset, therefore the tune switch has to be set permanantly on or it could not bring the frequency down. I'm thinking that it would probably be better to pull the HI band mixing crystal down by 3.75 Khz and then the tune switch could be rewired back to normal. This would then also allow correct operation of the tune pot when on UK band.
As for the switch, i hadn't planned on modifying the original, i had thought to get one from an old superstar or something - but now i learn that the shaft will be too short, i must get another idea. maybe some form of shaft extention. perhaps a tongue and groove with the shaft from another pot glued on to make the length...
How could anyone cut radio knobs in half to make them fit the radio, what a butcher!
I'll look tomorrow to see if i can see your ident anywhere on the eprom board
UPDATE: Here are better(?) pictures of the eprom board.
- eprom1.JPG (21.26 KiB) Viewed 19966 times
- eprom2.JPG (19.59 KiB) Viewed 19967 times
UPDATE 2 I have been looking into why the wires from the tune switch have been removed. When the radio is put in UK mode, the eprom is switched and also a resistor is switched in across the tune pot to give the UK offset, therefore the tune switch has to be set permanantly on or it could not bring the frequency down. I'm thinking that it would probably be better to pull the HI band mixing crystal down by 3.75 Khz and then the tune switch could be rewired back to normal. This would then also allow correct operation of the tune pot when on UK band.
Norm
Re: 88081 Eprom conversion board - any info?
Norm,
The Eprom board now looks to me like one of Spectrum communications Eprom boards with the 5v regulator soldered to the board and then screwed to the chassis to hold it in place and the number will probably be a date code.
The pull function on those controls is a complete waist of time, because of the amount of wire used to and from them it adds capacitance and therefore the frequency changes, so the radio is on one frequency with the switch in and another with it out, it just causes confusion as to why it's on frequency with it in and then when pulled out it's off and you have to start retuning again.
Just hard wire them both get rid of all the unnecessary wire and use the switches for some other function, like switching the beep and the alphas on and off, or the UK band if you don't want to alter the band switch.
When switching to the UK band using the rotary band switch you'll need an extra pole just to switch the KC shit to give the correct UK offset, by connecting the centre pin of the KC shit to that poles common and the output (when in the UK position) to a 5k resistor and then to 0v you can adjust the 5k to put the radio on the UK frequency making it unnecessary to retune the radio.
The other way is to use two crystals, one for all the FCC bands and the other just for the UK band, that way all you need do is to tune the UK crystal just for the UK band, less wires to fit.
Don't forget the Eprom can be erased and reprogrammed to whatever you want to put in it.
Dave.
The Eprom board now looks to me like one of Spectrum communications Eprom boards with the 5v regulator soldered to the board and then screwed to the chassis to hold it in place and the number will probably be a date code.
The pull function on those controls is a complete waist of time, because of the amount of wire used to and from them it adds capacitance and therefore the frequency changes, so the radio is on one frequency with the switch in and another with it out, it just causes confusion as to why it's on frequency with it in and then when pulled out it's off and you have to start retuning again.
Just hard wire them both get rid of all the unnecessary wire and use the switches for some other function, like switching the beep and the alphas on and off, or the UK band if you don't want to alter the band switch.
When switching to the UK band using the rotary band switch you'll need an extra pole just to switch the KC shit to give the correct UK offset, by connecting the centre pin of the KC shit to that poles common and the output (when in the UK position) to a 5k resistor and then to 0v you can adjust the 5k to put the radio on the UK frequency making it unnecessary to retune the radio.
The other way is to use two crystals, one for all the FCC bands and the other just for the UK band, that way all you need do is to tune the UK crystal just for the UK band, less wires to fit.
Don't forget the Eprom can be erased and reprogrammed to whatever you want to put in it.
Dave.
How far is it.
Twice it's length from halfway.
Twice it's length from halfway.
Re: 88081 Eprom conversion board - any info?
Dave, I think you nailed it! 
I went to the Spectrum Communications website and guess what? They do an eprom board called SC02A which just gives UK band in Cybernet Radios. I've sent Tony at Spectrum an e-mail to confirm this.
I'm sure i read somewhere about making a little circuit to switch between 2 crystals using some form of diode switching... I think i'll look into that for switching in the LoLo crystal, coz that will make things a lot neater. or maybe i'll just lose the LoLo altogether (its not like anyone uses that much anymore)
I just wanted to re-wire the pull switches to get the radio back as near to original as possible, but now i will have a rethink on that and maybe re-route the beep switch from the back of the radio...
UPDATE it has now been confirmed that the eprom in my Jumbo is A Spectrum Communications SC02A board which gives UK band only. So this is why the radio has a seperate LoLo mod.
I went to the Spectrum Communications website and guess what? They do an eprom board called SC02A which just gives UK band in Cybernet Radios. I've sent Tony at Spectrum an e-mail to confirm this.I'm sure i read somewhere about making a little circuit to switch between 2 crystals using some form of diode switching... I think i'll look into that for switching in the LoLo crystal, coz that will make things a lot neater. or maybe i'll just lose the LoLo altogether (its not like anyone uses that much anymore)
I just wanted to re-wire the pull switches to get the radio back as near to original as possible, but now i will have a rethink on that and maybe re-route the beep switch from the back of the radio...
UPDATE it has now been confirmed that the eprom in my Jumbo is A Spectrum Communications SC02A board which gives UK band only. So this is why the radio has a seperate LoLo mod.
Norm