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Korg poly-800 diode info

Korg poly-800 diode info

2019-01-31 by studio_1a@...

Hi, can someone give me some alternatives for D1=HZ-5CLL-TD and D2=SR1K-2 .  I noticed there are some differences between Klm-596-4 and Klm-596-8 unfortunately only general Klm-596 schematics are available.

thanks

Re: [korgpolyex] Korg poly-800 diode info

2019-01-31 by <backshall1@...>

I don’t think you would even see D1 on 596-8. It’s a zener diode that supplies power to the memory chip from the 6 C-cells when power is turned off. Since I believe version 8 had a factory installed CR2032 lithium cell between IC18 and IC 19 for memory backup, I think D1 and R1 were removed from the board. I don’t think I’ve ever seen a version 4. I saw a version 7 that had solder pads in the location where the lithium cell would eventually go, but no battery. It still had D1 and R1 on the board and they would have to be removed if you wanted to solder in your own battery. If they were not removed, the C-cells would attempt to recharge a non-rechargable lithium cell. Not a good idea. I have an old version 2 that has no solder pads for a battery, no room for the battery and no indication that they had thought about that yet. I think the only schematic available is for the old boards that include D1 and R1. I think D2 is just the “crowbar” diode to protect the voltage regulator circuits in case someone plugs in an AC adapter with center pin positive instead of center pin negative. It is regularly the first thing to burn up if you plug in the wrong adapter.
 
D1 is a 250mw (1/4 watt) zener, 4.8-5.3 volts. Any zener around 5v and at least 250mw should be good here.
D2 looks like a general purpose 1A rectifier
 
Don Backshall
 
Sent: Thursday, January 31, 2019 3:15 PM
Subject: [korgpolyex] Korg poly-800 diode info
 
 

Hi, can someone give me some alternatives for D1=HZ-5CLL-TD and D2=SR1K-2 .  I noticed there are some differences between Klm-596-4 and Klm-596-8 unfortunately only general Klm-596 schematics are available.

thanks

Re: Korg poly-800 diode info

2019-02-01 by studio_1a@...

Hi, you're correct about 596-8 only D2 is on the board w/2032 batt like you mentioned. But 596-4 does have both D1 & D2 thats why I was asking as the legs are gone on both components, so would 1n4001 for D2 and 1n4148 for D1 be ok?.
This 596-4 board is in really bad shape. Some transistors are not original either and I don't know if they are compatible namely Q1(2sb731), Q3(2sb744) and Q18(2sd794). I'm not sure that I could find those but would any readily available equivalent of those be suitable? Btw, would these parts be the same on other revisions as well? If you could let me know, thank you again

Re: [korgpolyex] Re: Korg poly-800 diode info

2019-02-01 by <backshall1@...>

1N4001 is fine for D2. 1N4148 is NOT the same thing at all for D1. Did you check to see if the solder pads are there between IC 18 and IC19, where a CR2032 could be installed? My preference would be to just add a battery there and remove D1 and R1 from the board. If you want to just leave it original and reinstall patches every time you turn it on, D1 would have to be a zener diode like the 1N5231C, 1N4733 or BZX55C5V1.
According to some old notes I have on my Poly 800 repairs, I once used a 2SB1314 to replace a 2SB731. I’ve replaced 2SB744 and 2SD794 on a Polysix and managed to find the right parts on eBay. I haven’t noticed any parts changing specs on different versions of the Poly-800 boards.
 
Don Backshall
 
Sent: Thursday, January 31, 2019 9:53 PM
Subject: [korgpolyex] Re: Korg poly-800 diode info
 
 

Hi, you're correct about 596-8 only D2 is on the board w/2032 batt like you mentioned. But 596-4 does have both D1 & D2 thats why I was asking as the legs are gone on both components, so would 1n4001 for D2 and 1n4148 for D1 be ok?.
This 596-4 board is in really bad shape. Some transistors are not original either and I don't know if they are compatible namely Q1(2sb731), Q3(2sb744) and Q18(2sd794). I'm not sure that I could find those but would any readily available equivalent of those be suitable? Btw, would these parts be the same on other revisions as well? If you could let me know, thank you again

Re: [korgpolyex] Re: Korg poly-800 diode info

2019-02-01 by studio_1a@...

Hi Don,

the 596-4 board does have a battery soldered and hotglued between IC18 & IC19 as well like previously mentioned D1 & R1 in place and soldered. The preference would be not to re-install the patches everytime, so then I should just remove D1 & R1 if the battery is present, hypothetical question could this have affected the -5 rail? I've measured the T1 transformer and will check the L1 coil next but all other rectifying diodes check out ok. On, transistors I've tried to cross reference those parts but some more obscure parts came up..I will try to source the original parts on ebay this way I won't have any doubts.


Re: [korgpolyex] Re: Korg poly-800 diode info

2019-02-01 by <backshall1@...>

I don’t see any way that D1/R1 and the CR2032 could affect the –5V rail. I think Q1 could mess up the ground line for both +5 and –5 and make them both look bad. Once D2 burns up and opens up, Q1 would be the next thing to go.
Don B.
 
Sent: Friday, February 1, 2019 12:10 PM
Subject: Re: [korgpolyex] Re: Korg poly-800 diode info
 
 

Hi Don,

the 596-4 board does have a battery soldered and hotglued between IC18 & IC19 as well like previously mentioned D1 & R1 in place and soldered. The preference would be not to re-install the patches everytime, so then I should just remove D1 & R1 if the battery is present, hypothetical question could this have affected the -5 rail? I've measured the T1 transformer and will check the L1 coil next but all other rectifying diodes check out ok. On, transistors I've tried to cross reference those parts but some more obscure parts came up..I will try to source the original parts on ebay this way I won't have any doubts.

 

Re: [korgpolyex] Re: Korg poly-800 diode info

2019-02-01 by studio_1a@...

Hi Don,

I believe that's why Q1,Q3,Q18 as well as various caps and other components were replaced, I just inherited this keyboard as non working(missing -5V rail?), but many things seems wrong. Questionable solder joints, ground leads to various components IC4-IC3 and some caps, really shitty work I must say done by previous owners, half desoldered CPU, new eprom...etc..I'm taking my time to review everything and clean it up,  hoping to revive it soon. I managed to order the original transistors from ebay, so its just a waiting game now.

Any other suggestions appreciated and thank you very much for your help. Have a great day