Kenwood 700M Relays?

Propar

Propar

Member
I've been searching for hours and other than a great general post from Echowars I can't find any information about what the replacements for the 3 relays on the Kenwood 700M protection board should be? Any help will be appreciated...

The relays click on when the power is switched on (no delay) and occasionally one of them sticks closed for about 5 minutes. It gets better the more the amp is used but I figure I might as well replace them...

Thanks...
 
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The two relays together on one side of the board are the speaker relays, as you have probably figured out. The replacements are Omron MY4-02-DC24, Digikey #Z2634-ND, and Mouser #653-MY4-02DC24.

The lone relay at the bottom is the soft-start relay. It is an Omron LY2-DC48, Digikey #Z2262-ND (they show only two in stock, but the Mouser PN is 653-LY2-DC48, just in case).

There's a 470µf 63V snap-in cap across the soft-start relay coils, designed to delay the closing of the contacts for a moment to allow charging of the power supply caps. I replace it with a 680µf 63V Panasonic TSHA, Digikey #P7469-ND. This slows it down a hair more, which I feel is beneficial.

Desoldering the speaker relays without destroying the foil traces takes patience, some solder wick, and solder paste to help the old solder flow to the wick. Kenwood bent the pins over on several of them, which is what makes it a PITA (I use the hot solder iron to break the bent pins loose after I get all the solder off of them). It takes real skill to prevent damaging the traces, but it can be done. Don't cut corners here...get the solder wick and paste before you tackle it.
 
Thanks!

I will order the parts right away and let you know how it goes. While I was searching the Forum, I actually ran across one of your posts detailing your method for removing parts without damaging the traces and I actually printed it out... so thanks for that as well. I've never worked on one of these Kenwoods before (ordinarily I would just send it to you... damn economy!). I would not have been aware of the delicacy of the traces, so the warning is much appreciated.

As always your generosity with information is really appreciated!
 
Replaced relays... mysterious green wire to driver transistors...

I finally replaced the relays with the recommended replacements and then read about replacing the driver transistors in one of Echowars posts (and now I can't find it)...

I can't find any replacements and was wondering what I could use?

Also there is a mysterious green wire soldered to the base of the Q-2 transistor (one of the above mentioned transistors) that runs to the front of the amp and attaches to a terminal strip with a couple of diodes and a capacitor. A blue wire comes off of that strip and seems to go to another terminal strip with a bunch of other blue wires that is above the right power meter? Any idea what that is for? I'm afraid that I messed up when I unsoldered the wire and I may have it wrong. I can't find anything on the schematics at all?

Any help will be appreciated...
 
The wire goes to the base of Qp2 on the protection board. The terminal strip & diode & chit are all there to force the relay to close ASAP when AC power is cut.

The stock design used the second section of the power switch to ground the relay drive when the power button is turned off (see the schematic and the two 56 ohm resistors near the transformer in the drawing, or just look at the power switch and the two resistors going from the switch to another terminal block down below it). This method works fine to open the relays when the amp is powered off using the switch, but if the amp is remotely powered (plugged into a preamp convenience outlet) or powered down with an AC power strip or some such (my amp is remotely powered through a Panamax AC protection unit), then the power switch doesn't get used, and the relays don't open till the power bleeds off, which can result in nasty transients to the speakers. Somewhere in the production run, a Kenwood engineer realized this, and this additional circuitry was added to force the relay to open as soon as AC power is cut, regardless of the position of the power switch.

I documented this, as well as the dimmer circuit, in the schematic below.
 

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Thanks again Glenn...

I really appreciate you clearing that up for me. Now I know why the wire was there and I can get it back in the right place...

While I have your attention, do you think it's necessary to replace the Qp2 and Qp3 transistors? The reason the relays had to be changed was that one of the channels wouldn't turn on until you tapped on the Protection Board. Once the amp was warmed up it worked normally (turning the amp on and off) but I also felt that the relays turned on too fast as well...

In the post (that I can no longer find) you recommended changing those two transistors. If you think I should, can you recommend replacements? I can't find anything that I know I can trust. Everything I can find has a different case style than the originals?

Thanks for any help you can give...
 
If the transistors were the reason the relays were giving you trouble, swapping the relays will not have fixed anything.

A couple of Zetex ZTX694B's will work fine here (but pay attention to the lead layout!! Download the data sheet and make sure you know which lead is which). Should replace the Dp9 diode too. A 1N4004 (or UF4004) will do fine.
 
Thanks again...

I don't know whether it was the relays or the transistors yet so I just ordered the parts and will change them out... Do I need to do anything about the heat sinks?

The reason I can't really test the relays is... This is one of my Trio units and it doesn't have the molex connectors and pins that the Kenwoods have. The board is just soldered in directly so I would rather just replace everything and put it back together only once...

Thanks again!
 
Also helps to know Kenwood's transistor marking on the boards. Easily visible when the holes are arranged in a circular pattern, but hard to make out when aligned in a row. This should help, but as always, check the schematic and the foil pattern when in doubt.
 

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Got it back together and it works!

I replaced all 3 relays, the driver transistors, the cap and the diode. Now both channels come on right away. The delay seems kind of short but I'm not hearing anything bad from the speakers so I'm satisfied...

Thanks for all the help! Really, it's kind of fun to fix this stuff as long as you have some great guidance... this forum is the best!

Thanks!
 
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