Essay
Active Member
Hello all,
I am the happy owner of 2 KA-8300 amps. Both amps are in working order, but of course, after 45 years, the electrolytics are reaching/past the end of their life and the power supply boards are in dire need of some conservation.
The information in this post is both from the forum, mainly the next threads:
https://audiokarma.org/forums/index.php?threads/spotlight-kenwood-ka-8300.868370/
https://audiokarma.org/forums/index.php?threads/kenwood-ka-8300-recap-list.997503/
https://audiokarma.org/forums/index.php?threads/kenwood-ka8300-power-supply-woes.756602/
https://audiokarma.org/forums/index.php?threads/kenwood-ka-8300-intro-pics-problems.698646/
https://audiokarma.org/forums/index.php?threads/kenwood-ka-8300-repair-help.639105/
And also from my own research and experience.
I have been doing some research on these amplifiers as the information is scattered over the forum (see links above). I intend to bring all information together in this thread so that other people with the same problem don't have to spend all the time on research I had to.
By the way, as I was doing the recap on my Pioneer SA-7500, I mentioned that I wouldn't touch the Kenwoods, but then I started checking on the recap, took the amps apart, and although they are quite a bit more challenging than the Pioneer, it appears feasable to perform a restoration without having to unsolder the board connections.
1) Disassembly
The disassembly of the KA-8300 is rather straightforward. The volume knob comes off after releasing the setscrews with a 1,5mm allen wrench. The other knobs can just be pulled off. The switch levers can be left on. Be careful upon removing the front plate as the pilot LED is fixed with a wire and a connector. This part might be fragile. The connector goes on with the red wire (+) on the long wire of the LED.
For accessing the power supply board, preamp and presence, the right power amplifier assembly (including heatsink) needs to be removed. It's a bit of a fiddle, but if you are careful, it works. You will notice that especially in the preamp, the components are really tight together.
2) Parts list (list will be updated based on your comments and availability on mouser)
I have listed my version of the parts list based on the repair manual and visual inspection of my unit. Comments are welcome. The list will be updated based on your comments.
- General
C1: 15 000µ, 63V, Diameter 52mm, height 85mm => Not much choice here, just take what is available from Nichicon (currently nothing)
C2: 15 000µ, 63V, Diameter 52mm, height 85mm => Not much choice here, just take what is available from Nichicon (currently nothing)
I wanted to fit a 18 000µ cap in it, but they have a larger diameter. I will stick with the existing value.
- Power supply board
This board has a very bad thermal design. There are many stories around the forum of cooked resistors and traces coming off. 1 of my amps is still rather OK while the other one has received some major work on this one. The restoration here is not limited to a recap. Resistors are beefed up to 3W mounted about 15mm off the board to improve on the thermal issues. I also intend to experiment increasing the value of R6 to 2,2K.
For the capacitors on this board, I intend to go with Nichicon UPM series, as they are high temperature (105°C). The lead spacing is also indicated. Unfortunately, today's electrolytics are generally smaller than the ones from 45 years ago, meaning that in most cases I was unable to respect that.
R1: 120R 3W => ROX3SJ120R
R2: 120R 3W => ROX3SJ120R
R3: 220R 3W => ROX3SJ220R
R4: 270R 3W => ROX3SJ270R
R5: 2K2 3W => ROX3SJ2K2
R6: 1K8 3W => ROX3SJ1K8 and ROX3SJ2K2
Dz1: Zener diode EQB01-28 => 1N5362B
Dz2: Zener diode EQB01-28 => 1N5362B
D3: Diode W06B => 1N4004
D4: Diode W06B => 1N4004
Qk2: 2SD415 => KSC2690AY
Ck3: 330µ 50V, 7.5mm => UPM1H331MHD6
Ck4: 330µ 35V, 7.5mm => UPM1H331MHD6
Ck5: 330µ 50V, 7.5mm => UPM1H331MHD6
Ck6: 330µ 35V, 7.5mm => UPM1H331MHD6
Ck7: 10µ 50V, 5mm => UPM1H100MDD1T
Ck8: 100µ 16V non-polar, 5mm => UEP1C101MPD (Only available 105°C capacitor)
Ck9: 100µ 25V, 5mm => UPM1V101MPD
- Power amp (order twice!)
In the power amp, I intend to go with Nichicon UKT, high temperature audio caps. Replace small caps with non-electrolytics.
Ce3: 1µ 50V, 3.5mm => MKS2B041001C00JO00
Ce4: 47µ63V, 5mm => UPM1K470MPD6TD or UPM1J470MPD1TA (No UKT available)
Ce5: 33µ 10V, 3.5mm => UKT1A330MDD or UKT0J331MED
Ce8: 330µ 63V, 5mm => UKT1A331MPD1TD
Ce9: 47µ 6,3V (10V installed), 5mm => UKT1A470MDD
Ce10: 47µ 6,3V (10V installed), 5mm => UKT1A470MDD
Ce12: 1µ 63V, 3.5mm => MKS2C041001F00JI00
Ce13: 1µ 63V, 3.5mm => MKS2C041001F00JI00
Qe1: 2SA750 E or F => KSA992FBU
Qe2: 2SA750 E or F => KSA992FBU
Qe1 and Qe2 will be matched and glued together.
Thermal paste for the TA-100Ws.
- Preamp
Here, I intend to go with Nichicon UKW series if available.
Cd1: 3,3µ 10V Tantalum, 3.5mm => MKS2B043301H00JSSD (Poly) or FK16X5R1C335K (Ceramic)
Cd2: 3,3µ 10V Tantalum, 3.5mm => MKS2B043301H00JSSD (Poly) or FK16X5R1C335K (Ceramic)
Cd9: 47µ 16V, 3.5mm => UKW1E470MDD
Cd10: 47µ 16V, 3.5mm => UKW1E470MDD
Cd11: 100µ 10V, 3.5mm => UKW1A101MDD
Cd12: 100µ 10V, 3.5mm => UKW1A101MDD
Cd15: 100µ 10V, 3.5mm => UKW1A101MDD
Cd16: 100µ 10V, 3.5mm => UKW1A101MDD
Cd23: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd24: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd25: 0,47µ 35V Tantalum, 3.5mm => RDER71H474K1P1H03B (ceramic)
Cd26: 0,47µ 35V Tantalum, 3.5mm => RDER71H474K1P1H03B (ceramic)
Cd27: 100µ 10V, 3.5mm => UKW1A101MDD
Cd28: 100µ 10V, 3.5mm => UKW1A101MDD
Cd33: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd34: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd37: 1µ 50V, grey, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd38: 1µ 50V, grey, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd47: 1µ 50V, orange, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd48: 1µ 50V, orange, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd51: 1µ 50V, grey, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd52: 1µ 50V, grey, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd53: 100µ 10V, 3.5mm => UKW1A101MDD
Cd54: 100µ 10V, 3.5mm => UKW1A101MDD
Cd55: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd56: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd57: 22µ 35V, 3.5mm => UKW1H220MDD
Cd58: 22µ 35V, 3.5mm => UKW1H220MDD
For replacement of the tantalums, I will order Tantalums as the space between the other components is very limited. If the Polymers fit, I will put them in, otherwise, I will stick to Tantalums. The 1µ caps will also be replaced with Polymers.
- Presence
Here, I intend to go with Nichicon UKW
Ci13: 1µ 50V orange, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Ci14: 1µ 50V orange, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Ci17: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Ci18: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Ci19: 100µ10V, 3.5mm => UKW1A101MDD
Ci20: 100µ10V, 3.5mm => UKW1A101MDD
- Meter amp
Here, I intend to go with Nichicon UPM
Cq3: 47µ 10V, 3.5mm => UPM1C470MDD1TD
Cq4: 47µ 10V, 3.5mm => UPM1C470MDD1TD
- Switch
Here, I intend to go with Nichicon UKW
Ch9: 1µ 35V Tantalum, 3.5mm => MKS2B041001C00JO00
Ch10: 1µ 35V Tantlaum, 3.5mm => MKS2B041001C00JO00
Ch11: 3.3µ 50V, 3.5mm => MKS2B043301H00JSSD (Poly) or RDER71H335K3M1H03A (ceramic)
Ch12: 3.3µ 50V, 3.5mm => MKS2B043301H00JSSD (Poly) or RDER71H335K3M1H03A (ceramic)
Ch13: 47µ 35V, 5mm => UKW1V470MDD
Ch14: 47µ 35V, 5mm => UKW1V470MDD
In cap values, there are only 2 deviations between the service manual and the amp (Ce9 and Ce10, where instead of 6,3V, 10V was installed). From the parts numbers, there is only 1 case where a certain Cap value has more than 1 part number, this means that they did not deviate capacitor types for a certain value except for 1µ 50V. There are 4 different part numbers, and after visual inspection, there are grey and orange caps. Because I intend to replace them with polymer film caps, I will not variate between the types.
3) Switches and potentiometers
Here, I am still in doubt about what to do. My (limited) experience is that Kenwood tend to be more scratchy than Pioneer.
I might have this part done professionally, as most of these items cannot be replaced once they break. Luckily, there is a repair shop not too far away that does this type of work. I have to go there anyway, as I also own a KT-8300 that needs to be realigned.
4) Carbon resistors
According to the service manual, this unit contains a lot of carbon resistors (basically less than 1W resistors are carbon). Is it worth to replace them with metal film, or do I leave them in?
5) Open topics
I have one question towards the specialists: I have seen that there are both Poly or Ceramic capacitors available for some smaller values. What shall I select there? What are the selection criteria between Ceramic and Poly?
Please let me know if you have any comments.
Is there a way to add pictures without having to go to an external server?
I am the happy owner of 2 KA-8300 amps. Both amps are in working order, but of course, after 45 years, the electrolytics are reaching/past the end of their life and the power supply boards are in dire need of some conservation.
The information in this post is both from the forum, mainly the next threads:
https://audiokarma.org/forums/index.php?threads/spotlight-kenwood-ka-8300.868370/
https://audiokarma.org/forums/index.php?threads/kenwood-ka-8300-recap-list.997503/
https://audiokarma.org/forums/index.php?threads/kenwood-ka8300-power-supply-woes.756602/
https://audiokarma.org/forums/index.php?threads/kenwood-ka-8300-intro-pics-problems.698646/
https://audiokarma.org/forums/index.php?threads/kenwood-ka-8300-repair-help.639105/
And also from my own research and experience.
I have been doing some research on these amplifiers as the information is scattered over the forum (see links above). I intend to bring all information together in this thread so that other people with the same problem don't have to spend all the time on research I had to.
By the way, as I was doing the recap on my Pioneer SA-7500, I mentioned that I wouldn't touch the Kenwoods, but then I started checking on the recap, took the amps apart, and although they are quite a bit more challenging than the Pioneer, it appears feasable to perform a restoration without having to unsolder the board connections.
1) Disassembly
The disassembly of the KA-8300 is rather straightforward. The volume knob comes off after releasing the setscrews with a 1,5mm allen wrench. The other knobs can just be pulled off. The switch levers can be left on. Be careful upon removing the front plate as the pilot LED is fixed with a wire and a connector. This part might be fragile. The connector goes on with the red wire (+) on the long wire of the LED.
For accessing the power supply board, preamp and presence, the right power amplifier assembly (including heatsink) needs to be removed. It's a bit of a fiddle, but if you are careful, it works. You will notice that especially in the preamp, the components are really tight together.
2) Parts list (list will be updated based on your comments and availability on mouser)
I have listed my version of the parts list based on the repair manual and visual inspection of my unit. Comments are welcome. The list will be updated based on your comments.
- General
C1: 15 000µ, 63V, Diameter 52mm, height 85mm => Not much choice here, just take what is available from Nichicon (currently nothing)
C2: 15 000µ, 63V, Diameter 52mm, height 85mm => Not much choice here, just take what is available from Nichicon (currently nothing)
I wanted to fit a 18 000µ cap in it, but they have a larger diameter. I will stick with the existing value.
- Power supply board
This board has a very bad thermal design. There are many stories around the forum of cooked resistors and traces coming off. 1 of my amps is still rather OK while the other one has received some major work on this one. The restoration here is not limited to a recap. Resistors are beefed up to 3W mounted about 15mm off the board to improve on the thermal issues. I also intend to experiment increasing the value of R6 to 2,2K.
For the capacitors on this board, I intend to go with Nichicon UPM series, as they are high temperature (105°C). The lead spacing is also indicated. Unfortunately, today's electrolytics are generally smaller than the ones from 45 years ago, meaning that in most cases I was unable to respect that.
R1: 120R 3W => ROX3SJ120R
R2: 120R 3W => ROX3SJ120R
R3: 220R 3W => ROX3SJ220R
R4: 270R 3W => ROX3SJ270R
R5: 2K2 3W => ROX3SJ2K2
R6: 1K8 3W => ROX3SJ1K8 and ROX3SJ2K2
Dz1: Zener diode EQB01-28 => 1N5362B
Dz2: Zener diode EQB01-28 => 1N5362B
D3: Diode W06B => 1N4004
D4: Diode W06B => 1N4004
Qk2: 2SD415 => KSC2690AY
Ck3: 330µ 50V, 7.5mm => UPM1H331MHD6
Ck4: 330µ 35V, 7.5mm => UPM1H331MHD6
Ck5: 330µ 50V, 7.5mm => UPM1H331MHD6
Ck6: 330µ 35V, 7.5mm => UPM1H331MHD6
Ck7: 10µ 50V, 5mm => UPM1H100MDD1T
Ck8: 100µ 16V non-polar, 5mm => UEP1C101MPD (Only available 105°C capacitor)
Ck9: 100µ 25V, 5mm => UPM1V101MPD
- Power amp (order twice!)
In the power amp, I intend to go with Nichicon UKT, high temperature audio caps. Replace small caps with non-electrolytics.
Ce3: 1µ 50V, 3.5mm => MKS2B041001C00JO00
Ce4: 47µ63V, 5mm => UPM1K470MPD6TD or UPM1J470MPD1TA (No UKT available)
Ce5: 33µ 10V, 3.5mm => UKT1A330MDD or UKT0J331MED
Ce8: 330µ 63V, 5mm => UKT1A331MPD1TD
Ce9: 47µ 6,3V (10V installed), 5mm => UKT1A470MDD
Ce10: 47µ 6,3V (10V installed), 5mm => UKT1A470MDD
Ce12: 1µ 63V, 3.5mm => MKS2C041001F00JI00
Ce13: 1µ 63V, 3.5mm => MKS2C041001F00JI00
Qe1: 2SA750 E or F => KSA992FBU
Qe2: 2SA750 E or F => KSA992FBU
Qe1 and Qe2 will be matched and glued together.
Thermal paste for the TA-100Ws.
- Preamp
Here, I intend to go with Nichicon UKW series if available.
Cd1: 3,3µ 10V Tantalum, 3.5mm => MKS2B043301H00JSSD (Poly) or FK16X5R1C335K (Ceramic)
Cd2: 3,3µ 10V Tantalum, 3.5mm => MKS2B043301H00JSSD (Poly) or FK16X5R1C335K (Ceramic)
Cd9: 47µ 16V, 3.5mm => UKW1E470MDD
Cd10: 47µ 16V, 3.5mm => UKW1E470MDD
Cd11: 100µ 10V, 3.5mm => UKW1A101MDD
Cd12: 100µ 10V, 3.5mm => UKW1A101MDD
Cd15: 100µ 10V, 3.5mm => UKW1A101MDD
Cd16: 100µ 10V, 3.5mm => UKW1A101MDD
Cd23: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd24: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd25: 0,47µ 35V Tantalum, 3.5mm => RDER71H474K1P1H03B (ceramic)
Cd26: 0,47µ 35V Tantalum, 3.5mm => RDER71H474K1P1H03B (ceramic)
Cd27: 100µ 10V, 3.5mm => UKW1A101MDD
Cd28: 100µ 10V, 3.5mm => UKW1A101MDD
Cd33: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd34: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd37: 1µ 50V, grey, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd38: 1µ 50V, grey, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd47: 1µ 50V, orange, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd48: 1µ 50V, orange, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd51: 1µ 50V, grey, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd52: 1µ 50V, grey, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Cd53: 100µ 10V, 3.5mm => UKW1A101MDD
Cd54: 100µ 10V, 3.5mm => UKW1A101MDD
Cd55: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd56: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Cd57: 22µ 35V, 3.5mm => UKW1H220MDD
Cd58: 22µ 35V, 3.5mm => UKW1H220MDD
For replacement of the tantalums, I will order Tantalums as the space between the other components is very limited. If the Polymers fit, I will put them in, otherwise, I will stick to Tantalums. The 1µ caps will also be replaced with Polymers.
- Presence
Here, I intend to go with Nichicon UKW
Ci13: 1µ 50V orange, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Ci14: 1µ 50V orange, 3.5mm => MKS2B041001C00JO00 (Poly) or SR215C105JAR (Ceramic)
Ci17: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Ci18: 10µ 25V, 3.5mm => UKT1E100MDD1TA
Ci19: 100µ10V, 3.5mm => UKW1A101MDD
Ci20: 100µ10V, 3.5mm => UKW1A101MDD
- Meter amp
Here, I intend to go with Nichicon UPM
Cq3: 47µ 10V, 3.5mm => UPM1C470MDD1TD
Cq4: 47µ 10V, 3.5mm => UPM1C470MDD1TD
- Switch
Here, I intend to go with Nichicon UKW
Ch9: 1µ 35V Tantalum, 3.5mm => MKS2B041001C00JO00
Ch10: 1µ 35V Tantlaum, 3.5mm => MKS2B041001C00JO00
Ch11: 3.3µ 50V, 3.5mm => MKS2B043301H00JSSD (Poly) or RDER71H335K3M1H03A (ceramic)
Ch12: 3.3µ 50V, 3.5mm => MKS2B043301H00JSSD (Poly) or RDER71H335K3M1H03A (ceramic)
Ch13: 47µ 35V, 5mm => UKW1V470MDD
Ch14: 47µ 35V, 5mm => UKW1V470MDD
In cap values, there are only 2 deviations between the service manual and the amp (Ce9 and Ce10, where instead of 6,3V, 10V was installed). From the parts numbers, there is only 1 case where a certain Cap value has more than 1 part number, this means that they did not deviate capacitor types for a certain value except for 1µ 50V. There are 4 different part numbers, and after visual inspection, there are grey and orange caps. Because I intend to replace them with polymer film caps, I will not variate between the types.
3) Switches and potentiometers
Here, I am still in doubt about what to do. My (limited) experience is that Kenwood tend to be more scratchy than Pioneer.
I might have this part done professionally, as most of these items cannot be replaced once they break. Luckily, there is a repair shop not too far away that does this type of work. I have to go there anyway, as I also own a KT-8300 that needs to be realigned.
4) Carbon resistors
According to the service manual, this unit contains a lot of carbon resistors (basically less than 1W resistors are carbon). Is it worth to replace them with metal film, or do I leave them in?
5) Open topics
I have one question towards the specialists: I have seen that there are both Poly or Ceramic capacitors available for some smaller values. What shall I select there? What are the selection criteria between Ceramic and Poly?
Please let me know if you have any comments.
Is there a way to add pictures without having to go to an external server?
