Your right, caps are a matter of taste
I do have some 4.7 and 10uf nichicon Muse caps, some Standart Elna ones
For now going to leave it like it is maybe put some bypass caps on the power supply diodes and main capacitors ( 0,1uf MKT ) just to see if I can lower the "noise" I ear when close to the speaker.
Thanks
Ric
I do have some 4.7 and 10uf nichicon Muse caps, some Standart Elna ones
For now going to leave it like it is maybe put some bypass caps on the power supply diodes and main capacitors ( 0,1uf MKT ) just to see if I can lower the "noise" I ear when close to the speaker.
Thanks
Ric
RS232
Good to hear that you have repaired the KL amp. I am a big fan of the amplifier and I hope you enjoy yours.
On my KL amplifiers the tantalum caps were only used to filter the power supply to each section of the amplifier being placed between the power supply rails and earth. I have never seen KL use a tantalum cap in line before. On all my amplifiers the in line capacitors are all plastic.
If I want more bass from the KL intergrated I normally assist the bass by partnering the amplifier with a Sony active subwoofer. This does not alter the KL amplifier output but just adds a little extra at the low end. The sony active sub woofers can normally be picked up on ebay for not much cash.
Don
Good to hear that you have repaired the KL amp. I am a big fan of the amplifier and I hope you enjoy yours.
On my KL amplifiers the tantalum caps were only used to filter the power supply to each section of the amplifier being placed between the power supply rails and earth. I have never seen KL use a tantalum cap in line before. On all my amplifiers the in line capacitors are all plastic.
If I want more bass from the KL intergrated I normally assist the bass by partnering the amplifier with a Sony active subwoofer. This does not alter the KL amplifier output but just adds a little extra at the low end. The sony active sub woofers can normally be picked up on ebay for not much cash.
Don
Thanks to all specially to might Zen
I know a schematic/service manual would be nice but... were to get one
I still have that "noise" from the power supply
What do you guys ( Zen Mod ? ) think about small MKT caps on the rectifiers and main caps I know it doesn't hurt but not an easy task to do in this amp.
There is an other issue I would like to fix but one thing at a time...
And look at this a visit from papa himself, I'm honored
Ric
I know a schematic/service manual would be nice but... were to get one
I still have that "noise" from the power supply
What do you guys ( Zen Mod ? ) think about small MKT caps on the rectifiers and main caps I know it doesn't hurt but not an easy task to do in this amp.
There is an other issue I would like to fix but one thing at a time...
And look at this a visit from papa himself, I'm honored
Ric
frankly , without schematic , there is slight possibility to point on culprit ..... is PSU or circuit itself prone to noise generating
usually , any snubbing (caps across diodes ) can be just cherry on top , not cure
anyway - if there is any sort of reg , try to change active/passive parts , to cure noise
if it remains the same ..... then circuit itself is to blame
on the other hand - counting that noise is same in both channels , it can be both - due to flaw in common PSU , or inherent to circuit construction
what's happening with noise level when you exclude pre-stage , as in test with CD ditto to pot ........ as I understood - pot is in usual place , between pre stage and , say, power amp ?
to be more precise - if noise is same in both min and max pot position , then culprit is after pot ..... so - look for common things between channels ....
usually , any snubbing (caps across diodes ) can be just cherry on top , not cure
anyway - if there is any sort of reg , try to change active/passive parts , to cure noise
if it remains the same ..... then circuit itself is to blame
on the other hand - counting that noise is same in both channels , it can be both - due to flaw in common PSU , or inherent to circuit construction
what's happening with noise level when you exclude pre-stage , as in test with CD ditto to pot ........ as I understood - pot is in usual place , between pre stage and , say, power amp ?
to be more precise - if noise is same in both min and max pot position , then culprit is after pot ..... so - look for common things between channels ....
Only the supply for the phono/input stage is regulated with 78L15/79L15 with one 200uf 100v cap and 2 10uf + 2 100nf near the regs ground is floating.
Noise is present with or without phono/input stage connected to volume pot.
Power supply is very simple: transfomer - rectifiers (8 of them) - main caps with 40000uf no snubbers anywhere.
The amp design is not the very best it still uses germanium transistores ( AC127/AC128 )and I think the rest of them (8 in total) are ZTX ones
And yes the noise doesn't change with pot position and the only common thing to both channels is the power supply.
I'm going to live with this noise for this weekend right now trying to fix a beautifull Marantz CD73.
Ric
Noise is present with or without phono/input stage connected to volume pot.
Power supply is very simple: transfomer - rectifiers (8 of them) - main caps with 40000uf no snubbers anywhere.
The amp design is not the very best it still uses germanium transistores ( AC127/AC128 )and I think the rest of them (8 in total) are ZTX ones
And yes the noise doesn't change with pot position and the only common thing to both channels is the power supply.
I'm going to live with this noise for this weekend right now trying to fix a beautifull Marantz CD73.
Ric
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Your KL amp probably has a seperate power supply for each channel; 4 rectifers per channel and 10 000uf per rail from a common transformer.
The ztx transistors are normal for KL. The ac127/8 I have never seen in a KL amp. The ztx transistors are usually in the vas or driver part of the circuit with a high quality transistor in the amplifier input; which is usually set up as an LTP.
Is it possible that someone changed some transistors sometime and put in the ac127/8 which could be the source of general background noise especially if in the amp input.
Don
The ztx transistors are normal for KL. The ac127/8 I have never seen in a KL amp. The ztx transistors are usually in the vas or driver part of the circuit with a high quality transistor in the amplifier input; which is usually set up as an LTP.
Is it possible that someone changed some transistors sometime and put in the ac127/8 which could be the source of general background noise especially if in the amp input.
Don
Hi AMV8
I don't think so, when I bought this amp it was faulty 2 of the rectifiers were shorted
I got that fixed and it worked fine untill a couple of weeks ago.
The board was unmolested all the solder points were original appart from the ones on the rectifiers that I replaced.
From what I could understand from the position of the transistor on the board the AC127/128 are the drivers for the power transistors (I didn't traced the tracks) but they are the last ones before the power stage.
Right now going to leave it as it is because I need to fix a vintage Marantz Cd73 for a friend and is starting to go on my nerves
I'm thinking in copy the board/schematic and post it here but like I sayed I need to fix the CD73 first.
Ric
I don't think so, when I bought this amp it was faulty 2 of the rectifiers were shorted
I got that fixed and it worked fine untill a couple of weeks ago.
The board was unmolested all the solder points were original appart from the ones on the rectifiers that I replaced.
From what I could understand from the position of the transistor on the board the AC127/128 are the drivers for the power transistors (I didn't traced the tracks) but they are the last ones before the power stage.
Right now going to leave it as it is because I need to fix a vintage Marantz Cd73 for a friend and is starting to go on my nerves
I'm thinking in copy the board/schematic and post it here but like I sayed I need to fix the CD73 first.
Ric
Hi, I need help with this integrated. I got one with some rectified diodes shorted. I replaced all rectifiers with better inverse peak voltage rating and all small elecrolytics (main power elcos are orginal) and some tantals. Amp is working fine but I have DC-offset in other channel -97mV what I don't like. Other channel has -29mV what I consider acceptable. DC-rails are +23,6V and -23,5V. There are two trimpots on the circuit board, are these for biasing or DC-offset? I have not adjusted them so far as I don't have schematic.
Hello friends of the forum,
I ask for your help because the kelvin labs I am about to restore suffers from background hum even with the potentiometer at minimum. This version has no pre-phono but only line inputs. In this thread especially the rs232 member was talking about the buzz problem but the discussion stops and I'd like to know how he solved the problem. I know it's been two years but it would help me a lot.
Also in the photo that I am attaching, I noticed that two zener diodes have been inserted in series, could you tell me the original value of the diode to be inserted?
I ask for your help because the kelvin labs I am about to restore suffers from background hum even with the potentiometer at minimum. This version has no pre-phono but only line inputs. In this thread especially the rs232 member was talking about the buzz problem but the discussion stops and I'd like to know how he solved the problem. I know it's been two years but it would help me a lot.
Also in the photo that I am attaching, I noticed that two zener diodes have been inserted in series, could you tell me the original value of the diode to be inserted?
An externally hosted image should be here but it was not working when we last tested it.
Hi Luciano63
I still have the KL and it still as the "hum" from the power supply.
I never got to the bottom of it because it never bothered me and of top of that I have to many amps at my disposal.
Back to the "hum" I tried everything and replaced the complete power supply section on the amp board and got nothing hum still there so i decided to live with it.
Does that one has germanium transistors ?
I still have the KL and it still as the "hum" from the power supply.
I never got to the bottom of it because it never bothered me and of top of that I have to many amps at my disposal.
Back to the "hum" I tried everything and replaced the complete power supply section on the amp board and got nothing hum still there so i decided to live with it.
Does that one has germanium transistors ?
Hi Ric,
thanks for your sharing.
I just ordered all the capacitors for the complete Recapp, the eight rectifier diodes with a 4 amp model.
Also on my KL there are the AC127 / AC128 germanium transistors and I thought to replace them with a couple of BC327 and BC337 (they look quite similar except the maximum Veb which is 5V instead of 10V). What else have you replaced in the power section?
Another doubt is about the pair of zener in the photo above. Someone has replaced them in place of the original one. What working voltage should the Zener have?
thanks for your sharing.
I just ordered all the capacitors for the complete Recapp, the eight rectifier diodes with a 4 amp model.
Also on my KL there are the AC127 / AC128 germanium transistors and I thought to replace them with a couple of BC327 and BC337 (they look quite similar except the maximum Veb which is 5V instead of 10V). What else have you replaced in the power section?
Another doubt is about the pair of zener in the photo above. Someone has replaced them in place of the original one. What working voltage should the Zener have?
Hi again
I don't remember what exactly but from memory I fix the faulty rectifiers (1N5404 3A 400V) main caps (10 000ufx35V) but don't remember if there were any polyester bypass ones.
I do remember that I had noise from the preamp power section and after replacing all caps it turned out to be the 78Lxx that was noisy (sorry don't remember exact voltage).
About the 2 zener diodes I had a look inside mine just after I answered your post and I also have 2 diodes on mine 1 BZX85C12 on top of the board and 1 BZX785V6 on the bottom side but they are connected in parallel (in your picture they are in series (?)).
Well now because of you i will have to sort this "hum" in mine too
Anybody know of a good replacement for the AC127/AC128 germanium transistors ?
I don't remember what exactly but from memory I fix the faulty rectifiers (1N5404 3A 400V) main caps (10 000ufx35V) but don't remember if there were any polyester bypass ones.
I do remember that I had noise from the preamp power section and after replacing all caps it turned out to be the 78Lxx that was noisy (sorry don't remember exact voltage).
About the 2 zener diodes I had a look inside mine just after I answered your post and I also have 2 diodes on mine 1 BZX85C12 on top of the board and 1 BZX785V6 on the bottom side but they are connected in parallel (in your picture they are in series (?)).
Well now because of you i will have to sort this "hum" in mine too
Anybody know of a good replacement for the AC127/AC128 germanium transistors ?
Hi Ric,
I'm glad to have an ally in the fight against buzz ...
On my KL, the two zener are in series but, from how they have been welded, it is clear that they have been clearly tampered with.
As seen in the photo, there is nothing at the bottom of the circuit.
The two zener are two BZX85C: one with a printed 12 and the other with a printed 20. At the moment I cannot measure the voltage across this series because I have disassembled the card but I assume it must be around 32 V.
This is very strange. It would be interesting to know what voltage you have across your zener in parallel.
I'm glad to have an ally in the fight against buzz ...
On my KL, the two zener are in series but, from how they have been welded, it is clear that they have been clearly tampered with.
As seen in the photo, there is nothing at the bottom of the circuit.
The two zener are two BZX85C: one with a printed 12 and the other with a printed 20. At the moment I cannot measure the voltage across this series because I have disassembled the card but I assume it must be around 32 V.
This is very strange. It would be interesting to know what voltage you have across your zener in parallel.