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Advice Recapping Hitachi SR-8010

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doctorly

New Member
I recently noticed a buzz coming out of my left-channel, through headphones and speakers, it's not loud.
The buzz stays the same volume regardless of the position of the volume knob.
I believe this is a newer issue, but it's also possible I just didn't notice it before.

I would like to recap this receiver anyway, as it's getting pretty old.

Should I only replace the electrolytic capacitors? Or are there other caps I should look out for?
Also I know there is an 'infamous' transistor in this unit that is known to cause noise, but I forget which one. Could someone look through 'ICS, FETS & TRANSISTORS' parts list on page 18 of the Service Manual to see if they recognize it?

Is the work required worth it for recapping the FM section as well?

I will probably do each section individually at different times and use the receiver in-between phases.

I really appreciate any advice and help you can give me, thanks in advance!

Here is a link to the service manual: https://www.hifiengine.com/manual_library/hitachi/sr8010.shtml
 
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My 2 cents on recapping.
Only replace electrolytics. You should also consider replacing the polar tantalum.
Check any fusible resistors and replace bias and dc offset trimmers with multi-turn types.
Yes, replace known problematic transistors. Wait for someone more knowledgeable on tuners for recap advice.

Replace 4 main filters with 6800/63V Nichicon KW
Use Nichicon PW for other power supply caps.
Nichicon EP for bi-polar power supply caps
Nichicon ES bipolar audio path
Nichicon KL for low noise/leakage in preamp/phono stage, to replace those orange/pale green...
Some prefer to use MKS2 film
Elna silmic II's for audio path and local power storage, Nichicon KZ is ok substitute

The 2sc458LG (rectangular/out-house shape) is problematic, replace with KSC1845.
 
mbz said:
My 2 cents on recapping.
Only replace electrolytics. You should also consider replacing the polar tantalum.
Check any fusible resistors and replace bias and dc offset trimmers with multi-turn types.
Yes, replace known problematic transistors. Wait for someone more knowledgeable on tuners for recap advice.

Replace 4 main filters with 6800/63V Nichicon KW
Use Nichicon PW for other power supply caps.
Nichicon EP for bi-polar power supply caps
Nichicon ES bipolar audio path
Nichicon KL for low noise/leakage in preamp/phono stage, to replace those orange/pale green...
Some prefer to use MKS2 film
Elna silmic II's for audio path and local power storage, Nichicon KZ is ok substitute

The 2sc458LG (rectangular/out-house shape) is problematic, replace with KSC1845.
Click to expand...

Wow, thanks a lot. I will go through these again and match the parts.

How come I want to replace the filters with 6800/63V instead of 2 4700uf/63V and 2 4700uf/35V like the original had?

I really appreciate all the advice, this helps a lot.
 
mbz said:
Use Nichicon PW for other power supply caps.
Nichicon EP for bi-polar power supply caps
Click to expand...

Is there a way for me to tell the type of polarity from the parts list in the manual?
I have only ever used the lengths of the leads to determine polarity.
 
doctorly said:
How come I want to replace the filters with 6800/63V instead of 2 4700uf/63V and 2 4700uf/35V like the original had?
Click to expand...
Provides slightly more energy reserves to better handle the (low) transients.

doctorly said:
Is there a way for me to tell the type of polarity from the parts list in the manual?
Click to expand...
Some schematics have a symbol key to explain the various parts, some add "BP".
The best method is look at what is currently in place and use same type.

doctorly said:
I have only ever used the lengths of the leads to determine polarity.
Click to expand...
The negative terminal is usually clearly marked, normally by a pale band
with arrows on the side of the cap.
upload_2018-8-1_8-10-54.png
Suggest resistance check fuse resistors like R713L, R715L, typically these
types drift high/out of spec, eg, a 47ohm could read >100ohms
 
mbz said:
Provides slightly more energy reserves to better handle the (low) transients.


Some schematics have a symbol key to explain the various parts, some add "BP".
The best method is look at what is currently in place and use same type.


The negative terminal is usually clearly marked, normally by a pale band
with arrows on the side of the cap.
View attachment 1248157
Suggest resistance check fuse resistors like R713L, R715L, typically these
types drift high/out of spec, eg, a 47ohm could read >100ohms
Click to expand...
OK, I went through the diagrams, compared them to the inside of the unit.
Almost all of the electrolytic caps are polarized, there are three that I am unsure about, they have no polarity marked on the PCB but they have this weird symbol on the diagrams.
 

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mbz said:
My 2 cents on recapping.
Only replace electrolytics. You should also consider replacing the polar tantalum.
Check any fusible resistors and replace bias and dc offset trimmers with multi-turn types.
Yes, replace known problematic transistors. Wait for someone more knowledgeable on tuners for recap advice.

Replace 4 main filters with 6800/63V Nichicon KW
Use Nichicon PW for other power supply caps.
Nichicon EP for bi-polar power supply caps
Nichicon ES bipolar audio path
Nichicon KL for low noise/leakage in preamp/phono stage, to replace those orange/pale green...
Some prefer to use MKS2 film
Elna silmic II's for audio path and local power storage, Nichicon KZ is ok substitute
Click to expand...

I am having a hard time with this.
How can I identify where the phono stage and preamp are?
The power supply seems easy, with the only cap I'm unsure about there being c504.

The manual lists "Audio Board", "Main Board", and "Sub Board".
I think the back half of the "Audio Board" where the transformer resides is the power supply.
 
Last edited:
I think that the phono stage is on the FM board.
Looks like it's the two circuits right in the middle of this picture. Does this look correct?
 

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OK, I also think that the front half of the Audio Board, that connects to the volume knob etc. AND the Main Board together comprise the preamp.
 
I posted a reply last night however its disappeared, so this may turn
out to be a duplicated.

The schematic is a logical connection diagram.
The board layout/artwork gives the physical layout.

Most schematics have flow from left to right and one channel under
the other. Most service manuals include a block diagram to give an
overall view.

On the schematic, the phono stage can be identified by starting with
the phono RCAs, eg PHONOL, starts at R402L(left) ends R409L/at the function
selector where the other inputs (AUX...) merge.

Path is then to S402a, S403a (switches, tape monitor,,,) to "L OUT 12"
Preamp starts at R651L volume pot, ends R612L. Power amp R701L.

This service manual groups the phono stage as "400" part numbers, likewise
pre(600), poweramp(700), protection circuit(500), power supply(800)

C504 as per pix.

Yes, phono stage as per your pix, 400 series parts.

C504.JPG
 
mbz said:
I posted a reply last night however its disappeared, so this may turn
out to be a duplicated.

The schematic is a logical connection diagram.
The board layout/artwork gives the physical layout.

Most schematics have flow from left to right and one channel under
the other. Most service manuals include a block diagram to give an
overall view.

On the schematic, the phono stage can be identified by starting with
the phono RCAs, eg PHONOL, starts at R402L(left) ends R409L/at the function
selector where the other inputs (AUX...) merge.

Path is then to S402a, S403a (switches, tape monitor,,,) to "L OUT 12"
Preamp starts at R651L volume pot, ends R612L. Power amp R701L.

This service manual groups the phono stage as "400" part numbers, likewise
pre(600), poweramp(700), protection circuit(500), power supply(800)

C504 as per pix.

Yes, phono stage as per your pix, 400 series parts.

View attachment 1250284
Click to expand...
I didn't think about correlating the part numbers with the stages, thanks a lot for all of the work you did.

So would you suggest not replacing the electrolytics in other stages? I have a few that look like they are part of something else now: c2xx and c9xx.
 
mbz said:
My 2 cents on recapping.
Only replace electrolytics. You should also consider replacing the polar tantalum.
Check any fusible resistors and replace bias and dc offset trimmers with multi-turn types.
Yes, replace known problematic transistors. Wait for someone more knowledgeable on tuners for recap advice.

Replace 4 main filters with 6800/63V Nichicon KW
Use Nichicon PW for other power supply caps.
Nichicon EP for bi-polar power supply caps
Nichicon ES bipolar audio path
Nichicon KL for low noise/leakage in preamp/phono stage, to replace those orange/pale green...
Some prefer to use MKS2 film
Elna silmic II's for audio path and local power storage, Nichicon KZ is ok substitute

The 2sc458LG (rectangular/out-house shape) is problematic, replace with KSC1845.
Click to expand...
Where would the Power Amp fall into in this list?
 
doctorly said:
So would you suggest not replacing the electrolytics in other stages?
Click to expand...
Depends what you are trying to achieve. Think you should be using the amp as a learning exercise. So what if you spend
a few extra $$$$'s on caps..

doctorly said:
Where would the Power Amp fall into in this list?
Click to expand...
Yeah, there are caps that should be candidates for replacement.
C701, 1uf/50V, either nichicon KL, MKS2 or Elna Silmic II's
C703, Silmic II's
:
You should diode/resistance test those diode chains D705-709, D710-714
 
While the caps are measuing "in-spec" it might be an issue with your capacitance meter, sometimes when the battery
runs down the accuracy can drift. I would have expected some of the 1uf caps to be out of spec, likewise some power
supply caps. That said, I've recapped a "few" vintage amps, I've come across 3 where there was only a slight improvevment
in sound quality (Luxman SQ-507X, SQ-700X, +?). I'm currently recapping a yamaha CX-1, all but 2 caps were in spec. No
rush to recap the CX-1000, sounds great as is. Point is, maybe your caps were ok and after recap maybe the difference
is subtle. Learn a bit also. Probably the difference is more noticable in vintage amps that used cheap caps, eg, NADS,,,
 
mbz said:
While the caps are measuing "in-spec" it might be an issue with your capacitance meter, sometimes when the battery
runs down the accuracy can drift. I would have expected some of the 1uf caps to be out of spec, likewise some power
supply caps. That said, I've recapped a "few" vintage amps, I've come across 3 where there was only a slight improvevment
in sound quality (Luxman SQ-507X, SQ-700X, +?). I'm currently recapping a yamaha CX-1, all but 2 caps were in spec. No
rush to recap the CX-1000, sounds great as is. Point is, maybe your caps were ok and after recap maybe the difference
is subtle. Learn a bit also. Probably the difference is more noticable in vintage amps that used cheap caps, eg, NADS,,,
Click to expand...

It's a brand new meter that came with new batteries. It's the Klein MM700. Also it only measures up to 4000uf so I couldn't measure the 4 filter caps. I was having a buzz in the left changed, so I'm sure one of those was severely out of spec.
 
Also I spent like 2+ hours recording the receiver with a mic against my speaker horns and woofers, so if there is a perceivable change we will definitely be able to tell. Obviously it's worth doing just to get rid of the buzz alone!

Replacing the noisy transistor will also help, right?
 
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