Model-FC-347 Model-FC-390 CRT/Super Star KF VI Frequency Counter (EPT210014D)

[TM007]

Just an observation while I was down a rabbit hole on something else.

Anyone else looking for hookup details for these or the same counter with the C rev board search using this link> What Dont you know about these counters?

Anyway many moons ago I tried and failed to hook one of these Rev D boards (EPT210014D) to a President Adams uPD858 7.8MHz. Lots of help from a busy community back then, but no joy.

Tried both pads JP1 & JP2
Tried 30pF and higher on the VCO tap.
Indeed tried a number of things but nothing completely worked. AM was always fine but USB & LSB were either USB ok or LSB ok but never both. Can't remember if there was an issue/difference between RX and TX, might have been.

The offset was always the issue, think it was 1.5KHz on a 7.8MHz radio, seemed fine on USB but not on LSB, weird, and never got to the bottom of it.
BUT I just re-read some of the threads in that search and saw the Lester Comms references about adding 18pF in the blank spot below the trimmer and some detail about swapping out some caps C13 & 14 for 1000pF.

Also read that there may be some length on hooking up the VCO to the Component side of the chosen radio rather than the solder side?

So I still have that Rev D EPT210014D (Both pads linked out) and I still have a relatively unadulterated Adams. So this is on my list of things to give another go, soon...in between arguing with A.I. .

Any further insights before I delve into this I'd very much appreciate the input as this isn't going to solved or helped by A.I. only human experience I suggest.

P.S. How did I get here? Well I thought there may be a way to read the ROM on the chip within the EPT210014D and then get the A.I. involved..... anyway highly unlikely to impossible as its got provision for read protection BUT I did find 2 interesting things out about that Microcontroller (HDLTEK HT48R50A-1)

1. It has an End of Life Date of 2027..... Data Sheet Not the best news given the volatility these packages can have.
2. They were used in Dentist Chairs..... who knew..... Your teeth are reading on frequency Mrs Smith!!!!

But seriously, any help before I delve in much appreciated.

 

[brandon7861]

Being the micro is the R series (HT48R50A), it is a one-time user programmable chip, so there is no reason to bother trying. The other version, the C, was mask rom and also not re-programmable. You would need a blank one.

It looks like the 74HC161 is being used as a divide by two and the micro gates it into the hardware event counter of the micro. Not that it matters though.

If it were me and I was set on using THAT counter housing, I'd gut it and stick something like a LS7366R and a ATmega4809 on a similar-sized board (with a TCXO for accurate gate timing) and reuse the same LEDs the original did. The LS7366R is a serial out 32-bit counter that can handle 40MHz in at 5v (so it needs no pre-scaling, kinda cool).

 

[19wrc333]

2. They were used in Dentist Chairs..... who knew..... Your teeth are reading on frequency Mrs Smith!!!!

Teeth are like crystals, if they are off frequency then you can file them a little bit with some dentistry tools to get them back on frequency.

OK.. I'll see myself out now.