Hello dear members,
First of all, I want to apologize for my English
I live in France and I restore vintage HIFI for many years (for my own)
(Here are some Youtube links
YouTube
YouTube
YouTube
YouTube
I had the opportunity to buy recently in Japan an Accuphase P-300S
I have already restored an Accuphase P-300 but the version "S" is different
I can not find anywhere the schématics and service manual on the internet (for adjustment points, BIAS, DC offset etc ...)
Please, can someone help me?
with many thanks
Alain
First of all, I want to apologize for my English
I live in France and I restore vintage HIFI for many years (for my own)
(Here are some Youtube links
YouTube
YouTube
YouTube
YouTube
I had the opportunity to buy recently in Japan an Accuphase P-300S
I have already restored an Accuphase P-300 but the version "S" is different
I can not find anywhere the schématics and service manual on the internet (for adjustment points, BIAS, DC offset etc ...)
Please, can someone help me?
with many thanks
Alain
Schematic wanted
I had this amplifier for troubleshooting on the weekend. Reason was a rattling of a relay on the PCB for level meter control.
This occurs because the electrolytics on this PCB in not good condition.
Also the electrolytics from the other PCB's I didn't like it anymore (year of manufacturing approximately 1980)
After replace all caps except the four large versions with 22mF/71VDC and two pcs 100uF BP on level meter control PCB the power amp works without any trouble - the rattle of the mentioned relay was disappeared.
After measuring the voltages follow question rises up:
1) on the big ELNA caps (22mF/71V - first image) I measure a voltage value between 70V3 and 71V8.
- is the real value for the voltage for this cap possibly 80VDC (usual are 63V, 80V and 100V - 71V are unusual) ?
2) 100uF BP (second image) - what alternative in better quality standart is available ?
3) variable resistor for the offset adjust only present on power amp PCB for left channel (in right channel not connected - go to the third and forth image). What is the reason therefore ?
Thank you for upload a schematic and some advices.
Description in detail concerning replacement and more photos will follow soon
I had this amplifier for troubleshooting on the weekend. Reason was a rattling of a relay on the PCB for level meter control.
This occurs because the electrolytics on this PCB in not good condition.
Also the electrolytics from the other PCB's I didn't like it anymore (year of manufacturing approximately 1980)
After replace all caps except the four large versions with 22mF/71VDC and two pcs 100uF BP on level meter control PCB the power amp works without any trouble - the rattle of the mentioned relay was disappeared.
After measuring the voltages follow question rises up:
1) on the big ELNA caps (22mF/71V - first image) I measure a voltage value between 70V3 and 71V8.
- is the real value for the voltage for this cap possibly 80VDC (usual are 63V, 80V and 100V - 71V are unusual) ?
2) 100uF BP (second image) - what alternative in better quality standart is available ?
3) variable resistor for the offset adjust only present on power amp PCB for left channel (in right channel not connected - go to the third and forth image). What is the reason therefore ?
Thank you for upload a schematic and some advices.
Description in detail concerning replacement and more photos will follow soon
Attachments
Last edited:
Japanese repaired the amp, you can check details inside.
accuphase p-300s
Below block diagram is from the brochure, it's quite good compare to P300 schematic.
I think the VR4 mainly control the power output BIAS. This is not a class A amp, so that Accuphase usually using low BIAS current per power trs. (maybe 8~10mA, you can set it similar to P300). You can test the power trs. emitter resistor voltage to calculate the BIAS current.
accuphase p-300s
Below block diagram is from the brochure, it's quite good compare to P300 schematic.
I think the VR4 mainly control the power output BIAS. This is not a class A amp, so that Accuphase usually using low BIAS current per power trs. (maybe 8~10mA, you can set it similar to P300). You can test the power trs. emitter resistor voltage to calculate the BIAS current.
Attachments
1. This cap is custom made, so that any value can do.
2. It's for meter only, so that any same value new cap is OK even no change, no change to sound.
3. VR is for DC servo fine tune only, if the overall circuit DC balance is good, so that VR no needed.
Thank you very much for this information.
I just note that the power amp from post #4 was not the one mentioned in the headline (model P-300S).
Rather, it is the P-300X - go to the last image from post #4 (completly an other version with multi emitter output power devices from Toshiba).
Thus I will start a new thread. Maybe the moderation can filed post #4 and #6 in the new thread under
https://www.diyaudio.com/forums/sol...00x-p300x-300-300s-schematic.html#post6095762
I just note that the power amp from post #4 was not the one mentioned in the headline (model P-300S).
Rather, it is the P-300X - go to the last image from post #4 (completly an other version with multi emitter output power devices from Toshiba).
Thus I will start a new thread. Maybe the moderation can filed post #4 and #6 in the new thread under
https://www.diyaudio.com/forums/sol...00x-p300x-300-300s-schematic.html#post6095762
Last edited:
Hi, regarding the bias settings for the P300S, as there's no available doc, I soldered 2 leads on the emitter resistor which is 1 ohm; to get 25mV or 25mA across the resistor then the reading on the volmeter between TP1 and TP2 is 50mV.
I've not yet found how to adjust VR2 for the feedback DC point. Should it be 0V measured on the speakers posts?
I've not yet found how to adjust VR2 for the feedback DC point. Should it be 0V measured on the speakers posts?