Harman Kardon HK 770

[argonrepublic]

This amplifier won't engage speaker relays or turn on meters until amp is warmed up. I am a novice but I am suspecting some worn caps. I can engage relays manually and no problem or warm up amplifier.

 

[Zen Mod]

replace C21, C22

 

[argonrepublic]

HK 770

I am absolutely amazed that you know just like that. Thank you very much.
Are there any mods or other things I should take care of while apart?

 

[Zen Mod]

Re: HK 770

I am absolutely amazed that you know just like that. Thank you very much.
Are there any mods or other things I should take care of while apart?

did you fixed it ?
after few decades in repairing biz , I had slight idea what's culprit

http://www.diyaudio.com/forums/showthread.php?postid=1668203#post1668203

 

[argonrepublic]

HK 770

Yes. I was looking toward the power being insufficient. Am I understanding correctly that these caps caused an excessive load? I didn't touch the amp prior to getting advice although I opened it.
I saw the site the other day with the HK 770. I was thinking that the Mono amp would be a nice Match to run Subs if I can find one.
Very nice site BTW.
What is your opinion on the HK 770? I bought it to run nearfield monitors on my desk. So far I am pleased but I often wonder if I am only hearing what I want to hear.
Thanks again.

 

[argonrepublic]

Hk 770

Obviously you know these amps well. I am contemplating pulling the HK 700 from my studio. Not for lack of quality but for convenience. I am contemplating replacing it with ART SLA-1 because of gain controls and balanced inputs. Mostly the attenuation though. I don't like decreasing volume digitally and sometimes this amp is a little too loud for my desktop speakers. Any suggestions or opinion on 700 Quality versus SLA-1?

 

[Zen Mod]

I'm not familiar with these SLA amps , so it's best that you organize direct comparison between your HK and SLA

I'll make some modifications to my own HK , because I'm not so satisfied with sound quality;

but - it isn't so bad comparing to many commercial amps of these days ...... it's just bad comparing it to some of best amps available to diy 😉

 

[mp9]

zen mod, i have a HK880vxi with a bad volume control which i'd like to replace with a alps, nobel or goldpoint but don't know what kohm to get. what would you suggest?

 

[argonrepublic]

Volume control

Along those same lines. What can I install in series to attenuate HK-770 without signal degradation?
What mods will clean it up?

 

[Zen Mod]

zen mod, i have a HK880vxi with a bad volume control which i'd like to replace with a alps, nobel or goldpoint but don't know what kohm to get. what would you suggest?

sorry - I can't find schematic of it , even with using already known trick with download link from HK ftp

I presume anything in range of 10-50K log will be adequate

 

[Zen Mod]

Along those same lines. What can I install in series to attenuate HK-770 without signal degradation?
What mods will clean it up?

probably plain voltage divider :

100K in line with signal , then 100K shunted to gnd

you'll have 6db attenuation

for mods - read here :

http://www.diyaudio.com/forums/showthread.php?t=133822

 

[mp9]

i think my hk 880 vxi may have a 100k volume pot because the print on it

reads 00202 - 100K (?) x2 , i can't make out what the (?) is but it's a smaller

text. i'll try again when i find the magnifying glass.

 

[Zen Mod]

i think my hk 880 vxi may have a 100k volume pot because the print on it

reads 00202 - 100K (?) x2 , i can't make out what the (?) is but it's a smaller

text. i'll try again when i find the magnifying glass.

can you measure resistance between to outer pins of pot?

 

[mp9]

i tried setting on kΩ and Ω, but didn't get a reading, it's mounted to a board along with a loudness switch which i plan on removing.
newbee question, was i supposed to do it with the power on and or did i use the wrong setting on my multi meter (it has: VDC VAC OHMS Ω with, >| -)))) (audio) symbols i don't understand, CAP,TEMP,FREQ%duty, µA, mA and A ac/dc)?

 

[Zen Mod]

i tried setting on kΩ and Ω, but didn't get a reading, it's mounted to a board along with a loudness switch which i plan on removing.
newbee question, was i supposed to do it with the power on and or did i use the wrong setting on my multi meter (it has: VDC VAC OHMS Ω with, >| -)))) (audio) symbols i don't understand, CAP,TEMP,FREQ%duty, µA, mA and A ac/dc)?

turn bloody thing off , and pull AC cord from wall ; you're risking death of you ,of amp , or both .

put multimeter in 200K range and try .

 

[mp9]

touching the the first and third wire of one of the (2), stereo wires from the innards to the board the volume pot is mounted on; 63.1 set @ k Ω .OL and 32.23 @ k Ω O.L for what ever reason it jumps around allot.
when i touch the two outer solder points of four located directly under the volume pot i get 12.50 @ O.L k Ω and 32.86 @ Ω from the first two solder points.

 

[argonrepublic]

attenuation HK 770

I reduce my output digitally by 8db, my decibels are nice, a comfortable volume but I lose dynamics and punch. Wondering if I should use a russound voulume control or if I can simply put a couple of high quality resistor in series on speaker cables. Should I attenuate the line level instead? Output is -10dbv

 

[gain wire]

well, you could convert both inputs (RCA) to SMA or BNC type connections install a fixed dB attenuator (few $), and have again SMa or BNC jacks to RCA...

a bit overkill, but those attenuators are made for RF and...


nevermind, it's 50ohms impedance, won't be good for your inputs... or outputs.

I gotta ask though, do you really think you'll hear the degradation of an added resistor in the signal path? I mean, come on!

I'd do what Zen Mod suggested in his last post.