The KA-2000 restoration

[Goldie99]

Check the schematics in the hfe service manual - yours should correspond to one of them.
Your voltages certainly seem a bit 'off' - I agree with eizner23, something's wrong.
Your voltages are not taken when using a DBT ?

 

[Zeromort]

 

[Zeromort]

After several checks and redone welds I obtain approximately these values which seem more correct.

 

[Goldie99]

Those look a lot better - the Q1 & Q4 values should be ca. half of the Q2 and Q3 values respectively, but with only the original open frame trimmers present I'd probably leave it like that rather than try to adjust closer.... or fit new trimmers first (see post # 14 & 28 in this thread).

 

[Zeromort]

ok.

 

[Zeromort]

With headphones the sound is very good. But when I connect speakers the sound is very bad, saturated and too distorted.

 

[eizner23]

Distortion out of finals-
Check health of the drivers- measure voltages on the pins of Q3-Q6, report back.
Check the bias-you measure millivolts across the emitters like this on both channels.

 

[eizner23]

Also Try HopJohns quote in post #20 to clen the headphone jack

 

[Zeromort]

Good morning
I set the BIAS to what value 14mv?

 

[eizner23]

 

[Zeromort]

I cleaned the contacts at the headphone input and the sound has improved significantly

 

[Zeromort]

Today I changed 2 2sc458 transistors on the MAIN AMP board and the sound has improved greatly

 

[Zeromort]

According to the diagram there is in parallel with the diode a capacitor of 0.22uf. On my amp there was none. Is it necessary to add it?

 

[eizner23]

I have no opinion other than you may have the Euro version to accommodate 220v-240v

 

[Butler]

Hi Zeromort, I have the KA-2000A 220-240v, just about the same as the KA-2000. Yes mine has the caps in parallel with the diodes



Hope this helps.

 

[iPhoneSasuke]

Thank for your post, It was very comfortable to use while writing part list. photos, ets.

You're been interested in replacing germanium on silicon. Look at KA-2000A SM. It's the same with usual KA-2000 but have different transistors: Qd 3,4 in PreAmp (2SC871) and Q 4,6 — 2SA565B (Si) instead of 2SB56A/2SB89A (Ge). The only difference I saw in other parts are caps Ce6,12 — 270p instead of 250p.