KR-9600 Restoration Info

hopjohn

Silver Face
I've read all the KR-9600 threads I could find here, but would like verification on a few things if anyone can help.

On each of the two power amp board it's been discussed that you should replace the differential pair Qe1 and Qe2 (2SC1345, ECB) with matching Zetex ZTX694B (noting CBE pinout) to get the DC offset as close to 0mv as possible. I assume all of the 4 hfe readings of the transistors are to be matched closely or is it just the individual pairs? I have 4 that are all read in the 745-760 range that I planned to use, but I also have 6 or so in the 1000-1285 range with scatterred readings. So which am I better off installing?

I've also seen noted as a preventative measure to replace Qe3 (2SC1775) with a ZTX694B, Qe6 and Qe7 (2SA912) with KSA1381, and Qe8 (2SC1885)with KSC3503. Are these each correct replacements?

Also does anyone source 8v 200ma mini bulb replacements for the four meter lights or do I need to improvise?

Thanks!
 
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The individual pairs should be as close as possible.

I've been using KSA1381 for Qe6 & 7 and KSC3503 for Qe8 with no problems.

There's an AKer that sources those here. DGWOJO is his nick. He has excellent feedback too.
 
Sorry, part of your answer is a bit vague. Let me reiterate what I'm wanting to know. Do the left channel Qe1 and Qe2 hfe readings need to match the right channel Qe1 and Qe2 hfe readings(all four matched) or can the left pair be well matched but different from a well matched pair on the right side?

Arbitrary example: Left 735,738 Right 831, 833 No good?

Also what about the Qe3 replacement, is ZTX694B a good fit?
 
Do the gain of the transistors in the amp in your den need to match the gain of the transistors in the amp in your family room? No...

Same deal here...the gain of the transistors in one channel do not need to match the gain of the transistors in the other.

FYI, the Zetex transistors are very good, but you must be careful in installation because of the center-base configuration of them, and the fact that Kenwood has the solder pads lined up in a row, expecting center-collector parts (which is why the 2SC2240BL is a nice part to use there as well).
 
Echowars, I've duly noted the CBE vs. BCE pinout. It's not new to me to have to manage pinouts to straight rows on the boards. I typically heavy bend pin 2(B) and 3(E) opposite directions of center and then sort of tuck pin 1(C) in between with a gentle bend making the straight row. I purchased 52 pieces of ZTX694B in hopes of getting some good pairs, knowing the drapes don't have to match the rug...umm yea makes things considerably easier.

I going to assume Qe3 can take a the ZTX694B, since no one is telling me different.
 
Thank you gentlemen for your help.

KR-9600 Restoration Notes:

Capacitor Methodology & Replacement for the KR-9600

A full KR-9600 cap list by AKer lha1992 can be found here Beware the link for the for the 1uf caps are for .1uf caps.

For starters, read Glenn's (Echowars ) cap replacement methodology.
The price of capacitors tends to fluctuate so I'll provide a guide, that way one might choose their own based on current pricing.

Power Supply and General Purpose Electrolytics, 105C
Panasonic FR - low esr, very low impedance
Panasonic FM - low esr, very low impedance
Panasonic FC - low impedance, smaller values than FM, FR
Nichicon HE - low impedance, long life
Nichicon PW - low impedance, long life, smaller values available than HE
Nichicon PM - typically larger lead spacing than PW
Nichicon KL - low leakage, shorter life, in 85C (2000h)& 105C (1000h)

Audio Grade Electrolytics, 85C, unless specified
Elna RFS Silmic II - "Silk Fibers"
Nichicon KZ Muse - "Premium Grade"
Nichicon FG Muse - Fine Gold "High Grade"
Nichicon KW "Standard, High quality"
Nichicon FW - "Standard Grade"
Nichicon KA - "High Grade" - 105C
Nichicon KT - "General Audio" - 105C

Bipolar/Non-polar Electrolytics
Nichicon ES Muze - on the large side, pretty green color.
Panasonic SU - typically smaller than Nichicon ES

General capacitor notes for the KR-9600
For all the 1uf 25v or 1uf 50v electrolytics & tantalums try 1uf 50v Panasonic ECQ-V1H105JL stacked polyester film caps as replacements.

Edit 2/15/15 : Sadly, the Panasonic ECQ-V1H105JL which I use frequently is being discontinued in March of 2015. As of now, quantities are still readily available, but when they are long gone you can use a CDE DSF050J105, unfortunately these are expensive at over a dollar a pop. Another option is the Wima MKS2 MKS2B041001C00KSSD which are +/-10%, not 5% like the others, but are only around .46 cents each.

I've pulled two 3.3uf 160v value caps from power amp boards of a stock unit, & not 100v as the list shows, but 100v can be used as Glenn mentions in post #9 since they are only seeing 69v tops.

A Nichicon ES Bipolar type cap WILL fit (100uf 16v) on the relay board (X13-2400-10) in this project. I mention this because often they are too large.

Main Filter Caps
The four large filter caps of the 9600 are 10,000uf 80v (40mm x 105mm). Panasonic ECE-T2AA123FA 12,000uf 100v (40mm x 80mm) from Digikey are a good fit. Glenn has also recommended part #338-2114-ND from Digikey. These have snap in terminals so crimp and solder round terminals to them.

Edit 3/31/16: The recommended main filter caps above seem to be no longer available. The best thing I can recommend that is widely available to date is the EKMH101VRT103MB80T 10,000uf 100v United Chemi-Con KMH (40mm x 80mm)



Parts Summary:
10,000uf 100v (x4) United Chemi-Con KMH EKMH101VRT103MB80T (40mm x 80mm)
Ring Terminals (x8) TE Connectivity 32185


mFcRd0M.jpg

A shot of the original filter caps and wiring before removal for reference. 33 years old with obvious signs of leaking.

kggAFAc.jpg

Two of the four filter caps ready for installation. Note the ring terminals soldered to the snap in pins. Craft foam is used (blue stuff) around one cap to provide a snugger fit.
 
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Also of note I pulled two 3.3uf 160v caps (Not 100v as the list shows) from each of the power amp boards.
100V is more than sufficient...these are just a local filter (and a damned small one at that) for the main rail voltages, which are only about 67~69V at idle.
 
Pre Amp

Pre Amp (X08-1540-10)


Cleaning
It's a good idea to clean the connector pins with deoxit while working on this board. I use the Deoxit D100L with needle applicator to put some on each pin and then use a q-tip to scrub them clean. Afterward, I apply a tiny bit more Deoxit and slide the connector on and off a half dozen times.

Edit: You might also try Brasso to remove any oxidation on the pins.
Edit2: I've tried the Brasso, it works really, really well. The pins now shine as new.

Capacitors
Cd1/2/28 (3.3uf 50v) to same, audio grade
Cd3/4/23/24 (100uf 10v) to same
Cd5/6/25/26 (47uf 10v) to same
Cd11/12/13/14 (2.2uf 50v) to same, audio grade
Cd27 (33uf 16v) to same
Cd31/32 (33uf 16v) to same, audio grade
Cd33/34 (470uf 35v) to same, 5mm lead spacing
Cd35/36/37/38 (1uf 50v) to 1uf 50v stacked poly Panasonic ECQ-V1H105JL

N9WBCt9.jpg

Pre Amp in original form.
4qtHjuj.jpg

Pre Amp with all new electrolytics and 1uf replaced with stacked polys.
 
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Tuner Board

Tuner/MPX board (X02-1100-10)

Capacitors
.22uf x2 Add stacked poly ECQ-V1H224JL2 (opamp pin 4 & 8 to ground)
Cb7/14/28 (1uf 25v) to 1uf 50v stacked polys
Cb38 (1.5uf 25v) to 1.5uf 50v electrolytic or stacked poly
Cb9 (2.2uf 16v) to 2.2uf 50v
Cb39 (3.3uf 25v) to 3.3uf 50v
Cb17/40/42/43 (4.7uf 25v) to same, audio grade
Cb47/51 (4.7uf 25v) Remove, replace with jumpers after opamp upgrade
Cb29/56 (10uf 16v ) to same
Cb33 (100uf 16v) to same
Cb36/60 (220uf 16v) to same

Cleaning the tuner cap.

This is essential, but needs to be done properly. Refer to the tuner forums sticky here.

Replacing the dated opamp.

The FM opamp ICb6 (NJM4558B) of the IF, MPX board (X02-1100-10) can be upgraded with excellent results. The original opamp is quite dated and was never of very high quality in the first place. Though there has been many suggestions for replacement, as of writing the Analog Devices AD823ANZ from Digikey seems a good choice. Remove the old opamp and install an 8 pin socket first like this so you can swap later on if you'd prefer and won't have to worry about heating the IC during installation. The opamp supply pins 4 (-V) and 8 (+V) should each receive .22uf bypass caps to ground. I installed these on the back of the board with insulated leads. Keep the leads from each supply pin to the cap as short as possible for best results. The lead length to ground isn't as essential.

Swapping Zener diode Dk4 14v 500ma (YZ-140) of the power supply board (X00-1830-10) with a 1N5242B (12V 1/2w) will help tweak the supply offset of the opamp. Having done all this you should be able to replace the output caps Cb47 and Cb51 (4.7uf 50v) with wire jumpers for improved sound.

If you are inclined to take the tuner a step further, the four ceramic filters ( CFb1, CFb2, CFb3, Cfb4 ) can also be improved upon with modern replacements and even an adder board. I'd only suggest this to those comfortable with doing tuner alignments as this will certainly be affected with any changes here.

Related link for further reading
 
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Power Amps

Power Amp boards ( X07-1480-10 )

Transistors
Since there is no adjustment for DC offset in the KR-9600 the best option to get close to 0mv in each channel is to replace Qe1 and Qe2 in the Left and Right power amp boards ( X07-1480-10 ) with a matching pair of Zetex ZTX694B. You need not match the hfe of all four replacement transistors just the individual pairs, but to do so you may need upwards of 25 pieces to get good pairs. You'll need a multi-meter that measures hfe. Harbor Freight offers a cheapo 7-function meter that will do the job. It's not uncommon to find ZTX694B with gain as high as 1100-1500. Try to find the closest matched, highest gain pairs you can for best results.

It's important to note the pinouts of these replacements. ZTX694B (CBE) are center-base and the original 2SC1345 (ECB) are center-collector. The power amp boards line up the pins in straight rows and it can be tricky to get the pins aligned properly. If you are new at this and are concerned about pinout being an issue for you consider using 2SC2240BL instead which use the same pinout (ECB) as the originals.

(Remember Left & Right Channels):
Replace Qe1,Qe2 -ZTX694B 25+ parts for matched pairs
Replace Qe3 x2 with ZTX694B
Replace Qe6, Qe7 x2 with KSA1381
Replace Qe8 x2 with KSC3503 (or 2SC3503)

Capacitors
Glenn suggests two 2.2uf back to back tantalum input caps on the power amp boards (X07-1480-10) should be replaced with one 1.5uf polypropylene cap and installed in the + holes on the board for best fit and to avoid using a jumper. Panasonic ECW-F2155JA (15mm lead spacing) works well here.

0NPWg7Y.jpg

Power Amp Board Before
TCu4P6K.jpg

Power Amp Board After
 
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Power Regulator

Power Regulator Board / Power Supply B (X00-1860-10)

This board is exposed to tremendous heat and needs attention. The Rr1 and Rr2 120 ohm 2W resistors ( sometimes beneath white spaghetti tubing ) at the top of this board get particularly hot and it is not uncommon to see scorching with weakned or even desoldered joints here. Glenn suggests removing Rr1 and Rr2 ( which are in parallel ) and replacing them with one aluminum cased 75 ohm 25W resistor mounted to the chassis wall behind the board. There is a small hole in the chassis wall just behind the board perfect for mounting this resistor. After applying some compound to the aluminum casing I use a small machine bolt and nut to hold it in place. It's also a good idea to replace the thermal compound on Qr1 and Qr2 as well to ensure maximum heat transfer.

AK member tarior took it a step further and replaced Rr3 and Rr4 with aluminum cased resistors as well.

Edit: Further discussion about replacing the Qr1/2 120 ohm 2 Watt resistors with the 75 ohm 25 watt aluminum cased resistor can be found here.

Parts Summary:
MG Chemical 860-60G Heat Transfer Compound 2 0z. jar
Replace Rr1,Rr2 with one 75ohm 25W Alum. Case Vishay/Dale RH02575R00FC02 or Stackpole KAL25FB75R0 (mount)
Replace Qr1 (2SC1419 or 2SD234) with On-Semi MJE15032G (apply compound)
Replace Qr2 (2SA755) with On-Semi MJE15033G (apply compound)

Optional
Replace Rr3 with 82ohm 25W Alum. Case Vishay/Dale RH02582R00FC02
Replace Rr4 with 120ohm 25 Alum. Case Vishay/Dale RH025120R0FC02

M71P4vl.jpg

Regulator board with R1 and R2 replaced with one 75 Ohm 25W aluminum cased resistor mounted to the chassis wall behind the board. Notice the browning of the PCB where the resistors had been. Especially at the inner pins where they were closest to R3 and R4.
 
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Power Supply

Power Supply (A) (X00-1830-10)

Replacement Parts if needed:
Qk5, Qk6 - Fairchild KSA733C (Mouser #512-KSA733CLTA)
Qk15 2SA809 to Fairchild KSA1381ESTU
Dk1 Zener Diode EQA01-35R 35V 1/2w; replace with two 1/2w Zener Diodes in series. 18+17= 35V, 1N5248B & 1N5247B
Dk2 Zener Diode, YZ-140(14V 1/2w); replace with Zener Diode 1N5244B (14V 1/2w)
Dk3 - Fairchild 1N4148 (Mouser #512-1N4148)
Dk4 YZ-140; use a 1N5242B (12V 1/2w) to even out the + - to within .5V difference (this was mentioned above in the replacing opamp section)
 
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Lamp Replacement

Lamps / Bulbs

The KR-9600 uses:
8v 50ma x9 (Indicators, Speaker Selection) available here WJOE.com
8v 300ma x 6 (AM/FM Dial) www.vintage-electronics.cc or dgwojo
8v 200ma x 4 (Meters) dgwojo

Want to try LED lighting? This thread can help. An addendum to the information found in this link/thread. Unlike the rest of the indicator lamps which run on DC, the speaker selection indicators are ~8v AC (check your unit for actual voltage, the last one I did was 7.4v). They run off the same source (54) as the dial lamps and meter lamps. The schematic below confirms this.

YZG5tv.jpg
 
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eBay'er whsh94a sells a LED kit for the 9600 that totally changes the look of the front of the 9600 from 'nice' to 'holy crap! that's great!'. Well worth the time and trouble. Ask for a red LED for the stereo beacon.

You don't mention the resulting voltages for the opamp supplies, or the resulting DC offset from the replacement AD823 (which looks like a nice part that I've overlooked through the years).

FYI, I use a Q-Tip and Brasso to clean the pins on the PC board, and shoot a small squirt of DeOxit into the female connector before plugging it in.
 
eBay'er whsh94a sells a LED kit for the 9600 that totally changes the look of the front of the 9600 from 'nice' to 'holy crap! that's great!'. Well worth the time and trouble. Ask for a red LED for the stereo beacon.

Thanks, I'll add the info.

You don't mention the resulting voltages for the opamp supplies, or the resulting DC offset from the replacement AD823 (which looks like a nice part that I've overlooked through the years).

I attempted to get the opamp supply voltages closer by changing Dk14 from 14v .5W to a 12v .5W as described in post #11. The results in the unit I have here are -13.09V at pin 4 and 12.77V at pin 8. This is well inside the .5v I was shooting for. DC offset isn't as good as I'd hoped. Left Channel Pin 1 is 4.6mv and right channel pin 7 is 2.9mv. Any suggestions for lowering it?

FYI, I use a Q-Tip and Brasso to clean the pins on the PC board, and shoot a small squirt of DeOxit into the female connector before plugging it in.

Yep, Brasso would work. I'll have to try it. Thanks.
 
I attempted to get the opamp supply voltages closer by changing Dk14 from 14v .5W to a 12v .5W as described in post #11. The results in the unit I have here are -13.09V at pin 4 and 12.77V at pin 8. This is well inside the .5v I was shooting for. DC offset isn't as good as I'd hoped. Left Channel Pin 1 is 4.6mv and right channel pin 7 is 2.9mv. Any suggestions for lowering it?.
It is what it is...if you balanced the supplies a little better, the results might have also been a bit better, but you're under 5mV, which ought to be good enough to eliminate the coupling caps.

The only way to lower the offset would be if you had a pile of opamps there and just kept popping one after the other in place to see which gave the best results. As it is, I think you're fine.
 
It is what it is...if you balanced the supplies a little better, the results might have also been a bit better, but you're under 5mV, which ought to be good enough to eliminate the coupling caps.

The only way to lower the offset would be if you had a pile of opamps there and just kept popping one after the other in place to see which gave the best results. As it is, I think you're fine.

I'll call it good then.

One question I have for you Glenn. I've done the power switch workaround on this unit as you described so well in this post The relay works, but has an annoying buzzing sound. In the first unit I did this to I don't recall having heard it. I thought it might be an isolated issue until I saw a follow up post, where an Aker had the same issue repeatedly. See post #28 in the thread I've linked above. Any other relay I could use that would perform the same task?
 
Seems some of these relays have issues with noise. I've run into one that buzzed. I just replaced it with one that didn't. I bench tested the rest of my stock (and you can do this as well before you install to save the trouble of removing it later) and the only noisy one was the one I already found.

There's nothing to prevent you from using any 120V relay that you choose, as long as coil current is nice and low, and the relay contact rating is as high as possible (I'd want at least 20~25A). I will not be buying any more of the Magnacraft relays, but I've not yet sourced a replacement (the Zettler relay linked at Amazon looks like an OK replacement, but I'm sure there are dozens of possible choices).
 
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