ARP 3620 clone project

[jamieoxford]

Looks great !

[julios]

Oh wow, relay cool

[ScottMcCandliss]

The cases are 9mm baltic birch plywood for the sides, 6mm baltic birch plywood for the large panels. ARP used some type of hardwood plywood in the same dimensions. It's not oak, but has a reddish color. Baltic birch is very strong, very stiff, and for weight to strength ratio, probably a better selection than oak.

The keyboard shroud is 9mm Baltic Birch plywood with solid poplar risers. ARP used their 9mm plywood and pine for risers. Poplar is much more resilient than pine and holds screws much better. Poplar is a hardwood, whereas pine is not.

Some of the builders gone by used MDF (advantageous for inexpensive kits due to hardness, flatness, and precise machineability, but very heavy, not very strong, and extremely sensitive to humidity and moisture). Others used pine, which is a softwood - not suitable for making box joints.



The corners are secured with 9mm box joints - very strong. ARP used 1/2" (12.52 mm) box joints for some reason, probably because it's a standard jig size. Matching the width of the teeth and notches in the box joint to the thickness of the wood provides optimum joint strength, so mine are stronger than ARP's.

The tolex was selected from several type of the same pattern, matched to the original from a 3620 to be identical to that used on the original.




Case hardware painstakingly sourced to be identical to original - mostly US NOS (New old stock). The open bore dimaeter in the rubber feet is a bit larger, but otherwise those are identical as well.



Original vs new handle


Tolex wrap used a one piece approach rather than ARP's three piece approach. ARP used animal glue, a favorite of factory production. However, one limitation is very short open time, hence using more pieces, meaning more seams. This tolex wrap is visually identical to the original except that the long seems close to the end edges are absent. The short vertical seams are the same. If someone insists on having the outer wrap be identical, I can do that. But as any owner of an ARP keyboard knows, it's more susceptible to coming loose with a long exposed overlapping seam. Many of them already have.






If anyone is interested in getting one of these, let me know and I'll put them up on reverb.

[dingebre]

I bought one from Scott. It’s excellent!!

David

[martimous]

Probably EXTREMELY late to the party, but any more of these available? Prints, drawings or the like?
I already did the TTSH build a while back, and would really like to do a 3620 to go with it.

[martimous]

Also, on the same or similar subject, has anyone had much luck trying to obtain a Fatar keybed? I tried to contact them a couple of times, and have never gotten a response back. I wasn't sure if they just did quantity or what. I've had a look at Kimber-Allen, and it doesn't seem like quite the same thing. I've also been restoring a Pro-Soloist, and I'm not quite sure if the OG 3620 keybed is the same sort of setup.

[Kipling]

Probably EXTREMELY late to the party, but any more of these available? Prints, drawings or the like?
I already did the TTSH build a while back, and would really like to do a 3620 to go with it.

Also, on the same or similar subject, has anyone had much luck trying to obtain a Fatar keybed? I tried to contact them a couple of times, and have never gotten a response back. I wasn't sure if they just did quantity or what. I've had a look at Kimber-Allen, and it doesn't seem like quite the same thing. I've also been restoring a Pro-Soloist, and I'm not quite sure if the OG 3620 keybed is the same sort of setup.

I have two spare PCBs for the 3620 at present but no front panels. The Pro-Soloist (I have one too) keybed has only a single contact per key whereas the 3620 requires two contacts per key (CV and Gate, with the CV contact closing momentarily before the Gate contact) or a Fatar keybed plus the decoder/relay PCBs. I believe Doepfer used to sell the Fatar keybeds, but they're not currently listed as available. Synthcube currently offer a 3-octave 37-key Fatar keybed with the possibility of other sizes in the future.

I have never had the opportunity to look at a Fatar close-up, so cannot comment on how easy (or otherwise) it may be to remove the bubble contact and matrix board assembly and add double contacts from another manufacturer such as Kimber Allen - see page 11 of their catalogue (part 1) https://315faa04-512c-4837-91de-84244c0 ... 6998dd.pdf. The photo shows the contacts fitted to the SKA keybed that Kimber Allen sold me in 2014

SKA 2.JPG (607.38 KiB) Viewed 406 times

[martimous]

I have two spare PCBs for the 3620 at present but no front panels.

Hey Kipling! Long time no see. I actually bought a PCB and front panel from you bleems ago and just have never built them up. I built up the TTSH and the ARP1601 sequencer that was offered here, but have never been able to find a suitable keybed. I got a Kimber-Allen catalog based on this thread, and that might be the way I wind up going. I have just heard the Fatar is the closest thing still in production to the old Pratt-Read keybeds of the wild days.
Thanks for the links/tips!!

[solar1]

Hi Folks,
For anyone interested, I may be able to help someone looking for a Pratt Read keyboard for their 3620 project.
It is a 61 note board.
PM me if interested.

[Kipling]

I have two spare PCBs at present but no panels. If anyone is interested in making their own front panel then I have created a Front Panel Express version of it, but it's quite pricey ($91 plus shipping each!). File attached.

[janvanvolt]

Also had the project in storage for quite a while now. Finished the main PCB, next waiting for the fatar decoder and relay pcb and then things go near the finishing line :-)

[Kipling]

And for anyone interested in building one who's not in the UK, it's cheaper to have five PCBs made by jlcpcb.com and shipped direct to you than me posting one overseas from the UK which is quite bizarre. The gerber files are attached. Simply create an account at jlcpcb.com and upload the zip file. You even get a discount on your first order.

The only issue is that I have 10 sets of the polycarbonate capacitors and the 6-pin chassis plug and line sockets required for the build here which I'd normally throw in with each PCB. I can of course send these at minimal cost to wherever they're required.

[ultravox]

And for anyone interested in building one who's not in the UK, it's cheaper to have five PCBs made by jlcpcb.com and shipped direct to you than me posting one overseas from the UK which is quite bizarre. The gerber files are attached. Simply create an account at jlcpcb.com and upload the zip file. You even get a discount on your first order.

The only issue is that I have 10 sets of the polycarbonate capacitors and the 6-pin chassis plug and line sockets required for the build here which I'd normally throw in with each PCB. I can of course send these at minimal cost to wherever they're required.

This is very generous Kipling, thank you for sharing.

[JanneI]

Yes, thanks a lot for sharing!

BTW: Does anyone know a place to buy that Kimber-Allen -type of keybed? Link?

[Kipling]

https://www.kimberallen.co.uk/

Not sure if they’ll have any left now as they were using up old stock when I bought mine in 2014. It’s the S.K.A. Italian keybed but it’s not listed in their catalogue, although worth asking them.

[musicorchard]

Thanks Kipling for the info!

I'm planning on a PCB purchase for the 3620 based on the files you included, but I would like to know who else would be interested. I'm based in the US so it makes more sense to mass buy the PCB and send them out to those who need them. Let me know and I can give you a base cost plus minimal shipping.

Kipling! I would be interested to buy any poly carbonate capacitors and 6 pin chassis plug and line sockets that you have for the build. Please reach out to me if you still have them available!

[Kipling]

Hi all

I've had a few enquiries for this lately. Sorry if I haven't responded to anyone yet - I've been busy on revising the 1601 sequencer. I'll be back on the case ASAP.

[kogz23]

I would like a pcb if anyone is going to do a group pcb order.

[kogz23]

I actually went ahead and ordered a PCB with the files provided. So I have 4 spare if anyone needs one.

[Kipling]

I actually went ahead and ordered a PCB with the files provided. So I have 4 spare if anyone needs one.

Are those the ones on Reverb at the moment? They may pull the ad as they’re quite strict on clones.

[kogz23]

No, it is not on Reverb. This is the only place I have offered them.

[Kipling]

No, it is not on Reverb. This is the only place I have offered them.

OK thanks. Someone has listed four boards and plated PCB panels on Reverb today. Quite cheap too.

[kogz23]

Damn, I should have just got those! I mighty see if I can get a panel off them.

[kogz23]

Actually I think I will go the FPE way. Speaking of which I just opened the file you posted and in my FPE the graphics are in black, so they can't be read. I am not familiar with the software. If I send them that file will the text be in white?
Thanks

[Kipling]

Actually I think I will go the FPE way. Speaking of which I just opened the file you posted and in my FPE the graphics are in black, so they can't be read. I am not familiar with the software. If I send them that file will the text be in white?
Thanks

The graphics look very dark in the software (edit mode) but if you do a 3D view or upload it to the FPE site it looks fine.

Edit: the graphics are in gold not white.