Hitachi SR 803 background noise

[cristi1media]

Hello,

I've just purchased a hitachi sr 803 receiver and today I’ve went and did some sound comparison between this and the other amplifiers that I have. The first thing that I've noticed was the background noise coming from it.

What I’ve noticed:

- it's not affected by the volume
- it is affected by the balance (the noise is more noticeable on the left channel vs on the right channel)
- the high filter reduces it (but not much)
- the noise is present on all sources

Any thoughts? I'm not so skilled with electronics but I am able to change something if known what.

 

[redk9258]

Welcome! That's a beautiful receiver! Hiss could be noisy transistors or maybe old caps? Has this been used consistently or sat unused for some time? If it sat unused for some time I would run it for a while and revisit the hiss later.

 

[cristi1media]

Well from what I know from the previous owner this has been sitting for some years powered off.
For now the first impressions are the it rocks on the FM band - compared to other receivers from that area ('70-'80)


This is how it looks without the cover, I was thinking to start with replacing first those two power source caps but for now I will take you advice and run it for a while.




Also, that heatsink is getting really hot and is elliminating a lot of smell )

 

[cristi1media]

Hello, I need a little help, I want to replace the tranzistors from the pre-tone board, but I don't know how to search for some equivalents.
It has 4x 2SC1344 and 2x 2SA673

Can you please help me in identifiing something equivalent?



I am planning a full recap for this amp (this would be my first project this big) and considering that I want to change those transistors as well.
Thank you.

 

[cristi1media]

Well, just got another hitachi today
It's basically the same on the inside... and this one has some background noise but it's at normal level and also it's the same on both channels

 

[ryuuoh]

Not the 803, but close enough I think:
https://audiokarma.org/forums/index.php?threads/hitachi-sr-903-restoration.763465/

 

[cristi1media]

Well, after doing a full recap on the SR 803 (paid someone to professionally do it - only used Nichicon FG and some FW - and Sanyo for the power supply section) the noise on the left channel is still present.
I'm getting really tired and angry with this receiver.... I'm out of ideas.
Side note : The other Hitachi that I have (the SR802) doesn't have that background noise and all the capacitors all original..

Any ideas? Should I start changing the transistors?

 

[cristi1media]

I've finally got rid of the hiss.
Changed the 4x2SC1344 transistors from the pre tone board and both channels are very quiet now. Actually those are listed in the top 10 worst transistors thread.
I've used 2N3711 as replacements (these were in stock on mouser and also recommended as replacements).

Posting this reply thinking that maybe it will be helpful for someone.

And as an impression, after the recap the SR 803 come to life, the sound is really nice.
Now I'm doing the same for the 802.

 

[cristi1media]

Some updates: Both 802 and 803 are fully recapped and the bad 2Sc1344 changed (28 in total for both).

Posting some photos with the progress and final results


The main filter caps were replaced with kemet - 2 x 15000 uF for both insted of the original 12000

 

[cfinchrist]

How does it sound now?