Trio KA-4002a - Now arrived/needing help

oldgringo · Jul 4, 2011

Trio KA-4002a - Now arrived [+ help required pls.]

Just taken delivery of 'one-off' of the above, per an earlier post. As said by others, one way or another: 'This amp has no right to sound this good' :banana:

However, after checking it for hums and 'scratchyness' [of which there are zero - at all volume levels]; and playing half a dozen cd's, which had me in absolute raptures, I plugged in the 'Grado's'. Only one channel could be heard through the phono receptacle. I went through the process of eliminating my questions around the headphones, then decided to take off the 'lid' and look at the connections. One connection was indeed cast adrift, amongst the dust [NOT smokey-dust though - one blessing!] - of which 'this-has-it's-fair-share'. So, how to reconnect the phono circuit [???]. I could not see very far into the back end of the receptacle; and noting another spade-type clip already taking up most of the internal space, spent half an hour trying to get the connector clip 'slotted-in' or 'on'. So I'm now questioning how these connectors are attached [me residing at the lower end of a scale covering 'amateur' to 'klutz'!]. Can anyone help here please; and should I use anything stronger than a camera-blower canister to blow away the dust before applying Deoxit [or it's UK equivalent]???

Cheers, Dave :thmbsp:

Robisme · Jul 6, 2011

Is that the headphone jack? It looks broken. I may have one.

I have a KA-4002. Same amp, cheaper build.

I had a parts unit too. I will look around.

If yours is not broken, let me know.

Rob

oldgringo · Jul 6, 2011

Thanks for the response, Rob! I got into this with the seller. What looked like a crack, all but disappeared when I wiped off [some of

] the dust. Anyway, please find three more pics, which may shed further light on the subject when viewed by someone who actually knows something about what he/she is 'lookin-at'

.

Mini update [during 'upload']: It looks more like a crack, this a.m. [UK] - but still, I am yet to account for the loose connection [Also the new views show a previously unnoticed/yet to be recognized 'spade' connector].

Cheers, Dave :thmbsp:

oldgringo · Jul 6, 2011

I also attach a 'detail' of the schematic diagram [I have the whole 5.6 meg document, if anyone is interested], which covers the subject location in case this helps [I don't understand the references to both Stereo and mono, here, either

]

Cheers, Dave :thmbsp:

Oilmaster · Jul 6, 2011

Dave,

In addition of Rob's offer, I could also offer a spare jack, as I recently demolished a KA-2002 unit for parts. The 2002 and 4002 models are quite identical; the 4002 series having slightly higher rail voltage and larger output transistors, plus additonal knob for speaker selection. The rest is almost identical. I also have two 4002A units myself; nice sounding amps indeed.

As you can see at the second picture of post #3, the black molded housing of the jack has a crack, indicating IMO that this unit has once had an incident where a large force was applied to a male jack sticking into the unit. The female jack is probably lost.

Hence, you will have to dismantle this jack. This is quite easy:
- pull off all the round knobs (yes, just pull)
- remove the little screws on the top and the bottom of the aluminium faceplate
- remove the hexagon nut(s) around one (or 2) shafts
- then the faceplate should be free to pull it off the chassis.
- then you have access to the headphone jack: remove the hexagon nut on the front side, and you can pull it away from the back side.

Then please post some new pics from various angles of the jack. You (we) can then assess whether the jack is beyond repair or not.

Concerning the mono 'thing'.... During the era this unit was built (~1974), it was still quite normal to have mono signals (in and/or outputs). What you see on the schematic is a rather brutal way of mixing left and right channel into a combined mono signal; they just 'tap' both signals from the speaker output signals via a resistance and knot them together. It's a notorious source of crosstalk and unwanted ground loops; this post reminds me to remove these resistors when I will rebuild my 4002A's in future.

Ozzy

oldgringo · Jul 6, 2011

Wow, thanks there, Ozzy! Just got in [10:00 pm-ish] and now plan to get into proving whether or not the 'molded housing' is cracked or scratched [I'll probably get to it tomorrow a.m. following a much needed (by 'yours truly') cleaning!]. Meanwhile do you/anybody know what the loose connecting wire and fixed 'empty' spade connector are 'all about', per the following:

oldgringo said:
Mini update [during 'upload']: It looks more like a crack, this a.m. [UK] - but still, I am yet to account for the loose connection [Also the new views show a previously unnoticed/yet to be recognized 'spade' connector].

Like could these be the result of any 'accident' or is there another explanation?

Also, feel free to comment on the last set of pics, Rob.

Cheers, Dave :thmbsp:

Oilmaster · Jul 6, 2011

IMO, so far the current pictures can show, the spade used to be inside the black moulded block, and you (or previous owner) pushed it outside when putting in a male jack. Yes, I think this is the result of an accident where a sudden side-way force was applied to a headphone plug, like somebody walking by. Things like that happen.

oldgringo · Jul 6, 2011

Quite possible! I'll try to get more pics out tomorrow for further 'eagle-eyed' scrutiny.

Cheers, Dave :thmbsp:

oldgringo · Jul 7, 2011

I now feel like I'm back in 'pre-school' [which will soon pass], because the knobs don't want to come off

- well, three of them anyway. The three 'sound-adjusters' [Bass, Treble, Balance] will just slide off, no prob. The Speaker-selector, Volume [surprisingly, to me] and Source knobs need quite a lot of pressure to move them just a smidgen which, after moving, are pulled back by some component that is resisting the extraction - something creating a 'spring-loaded' effect.
It would be too easy for me to bust them, if this model/version employs some other method of securing certain knobs.
So this is to double-check that I can indeed just give 'em a [respectful] yank.

Cheers, Dave :thmbsp:

Oilmaster · Jul 7, 2011

Hi dave,
Well, from the factory there are no locking screws, else you would see a small threaded hole on the side of the knob (with a little screw head at the bottom of the hole). They are just splined shafts. Sometimes Kenwood did put a small piece of fine/mazed white fabric around the shaft, so that the knobs would stick better (look inside the knobs you already took off). What might be a trouble maker, is in case a previous owner had the problem with the knobs coming off, and he/she decided to put some glue (or something else) on it. Perhaps you can see some glue remains on the shafts of which the knobs do not want to come off? Well, what to do? Perhaps spraying some WD-40 on the shaft behind the knob, to loosen/solve the glue a bit? I would not like to suggest things resulting in damaging the pots, but you can actually pull quite a lot (not unlimited though), but only pull in a straight line forward, do never start twisting the knob up and down at the same time: the shafts are often made of aluminium, they might break off ! Putting some flat surface (like solid dining knives) at two sides (to avoid unequal force) behind the knob may do the trick, though put something under the knives as well to avoid damaging the faceplate !
Ozzy

oldgringo · Jul 7, 2011

Cheers Ozzy!

Will try all of the above, carefully. I cleaned her up nicely; and she's too nice-sounding to spoil with lack of knowledge.

Dave :thmbsp:

oldgringo · Jul 8, 2011

Many thanks Ozzy, for getting me at least this far! The knobs came off with a bit more 'pull' - the stubborn ones had some kind of [now] black powdery deposit inside the splines. Glue residue? Very likely. And the shafts have a pretty significant 'spread-slot', down their length, which gives [in my limited experience] above average 'grip'.
So, the 'Molded Housing' is broken [please see pics 1 and 2]. This brings up an interesting issue: Replacing it will give me a possibly less than satisfactory 'Mono' headphone source ["It's a notorious source of crosstalk and unwanted ground loops"]. I should get this done to preserve the integrity of the piece; but as I wanted this unit for 'PC' sound, I'll have to put my thinking cap on again in order to get 'stereo' sound amplification for my [occasionally-used] headphones. This now turns out to be another item for me to identify, before purchasing a vintage amp! And, I am definitely interested in following up on your mention of you having a spare 'jack'.

Cheers, Dave :thmbsp:

Oilmaster · Jul 8, 2011

No, you won't have mono headphone; it will be (is) stereo allright. What I tried to explain is that a mono OUT is created by tapping off the left and right amplifier output signals (to speakers and to headphone) via resistors, and then knotting them together. Hence, the headphone output is real stereo, no worries, and you don't have to modify anything (my remark was for the purist, forget about it). I also use this amp as my PC desktop amp, and connect my headphones to it regularily; it sounds fine as is. You only need to replace the headphone jack. Inbound PM.

oldgringo · Jul 8, 2011

Hi Ozzy,
PM read, really appreciated and 'replied-to'. This has been a really great help to me and I look forward to replacing the housing. I was on the verge of returning the little TRIO, till 'AK' came to the rescue - again!
Btw, I am a 'purist' - I only drink Guinness and, occasionally 'Bathams' - when I can get it

Cheers, Dave :thmbsp:

Oilmaster · Jul 17, 2011

oldgringo said:
Btw, I am a 'purist' - I only drink Guinness and, occasionally 'Bathams' - when I can get it

You mean this Bathams ? Never seen/drank that on the continental shelf here :no:

, and I'm really into (continental

) beers... Do they serve that somewhere in London as well? I've gotta go there in a couple of weeks.

Bon, back home from sunny/rainy Brittany. Do you still need a jack? The one of my late KA-2002 is actually a bit different, because it serves as a speaker cut-off when a headphone plug is put in (the 4002 amp has a dedicated selector switch for this). Still, no problem, because I also have some normal jacks like yours from former Sony units; they are very simular and should fit. I should make and post a picture this weekend.

oldgringo · Jul 17, 2011

Hi Ozzy!
Yes, 'that' Bathams. It's not sold too far away from it's 11 'core' pubs and 18 or 20 'guest' pubs and small 're-seller' breweries. I have to nip over from Birmingham, into the 'Black Country' [which is an old industrial area of approx. 20 miles X 5 miles - http://en.wikipedia.org/wiki/Black_Country ] to partake of their fine brew(s)! ['slurrp'!

]. This being a mammoth '10' miles away

.
OK, I've not managed to get the correct 'Jack Socket' [as they call it in these parts], yet. I did get close - the size of the body of the casing has been matched but the dia. and the length of the threaded part are proving to be more difficult. The hole diameter in the chassis is 9 mil; and the smallest thread dia, so far, is 9.2. I've located a version stocked by a US supplier; but haven't 'squeezed-the-trigger' on that one yet.
One thing that I have done [being a 'purist'

], is, upon noticing that the connection that had been broken free, would 'partly' slot back into the casing - but with no 'back-wall' to support it, I 'dripped' a large 'blob' of a quite strong glue, into the 'breach' [dear friends

], waited a day, then tried-out the resulting 're-assembly'. It's holding, for now :beerchug:

. It's also supplying 'very-nice' stereo-sound to the headphone jack :music:

- for now; but I still have to press on with this exercise, right? :yes: . So I'll continue to 'beat-the-bushes' here for a while; and keep you posted.

Thank you for 'staying-tuned'.

Cheers, Dave :thmbsp:

Oilmaster · Jul 18, 2011

Hi Dave,

Actually, I was thinking about if you could do that rebuilding with glue; seems you did it already. I dived into the boxes and cabinets with parts, and the Sony sockets are actually sort of flange mounted, hence no threaded shaft. Indeed, the shaft measures 9.0 mm (M9 fine thread), and several other sockets I have are all larger. The only one I have is from the KA-2002. In case the current solution doesn’t hold, and you have a close-matching one, then you could always enlarge the hole in the chassis by filing or drilling. Eventually, I could send you mine.

Thanks for the wiki link on the Black Country, because I was wondering for some time what it was about: "in the 19th century this area had become one of the most intensely industrialised in the nation. The South Staffordshire coal mines, the coal coking operations, and the iron foundries and steel mills that used the local coal to fire their furnaces, produced a level of air pollution that had few equals anywhere in the world. It is popularly believed that the area got its name because of pollution from these heavy industries that covered the area in black soot". Apparently some beer too…

Also, would it be linked to the fabulous rock group Black Country Communion (with Joe Bonamassa and Jason Bonham) ? Talking about that rock group, I discovered them thanks to the best classic rock station in the world: Planet Rock, and thank god for internet. Another blessing from that island :thmbsp:. Note the event news about the beer festival in London; gotta make sure my business trip to London will be that week. Again that ‘CAMRA’ thing… Is Real Ale under thread?

To stay to the thread’s topic: that’s exactly the radio station making many hours each day through my KA-4002A…

Back to off-topic

: will pass Belgium next week on my way visiting family in Holland, of course making the ‘usual beer stop’ in Belgium. This time hopefully to pick up the best Trappist beer ever: Westvleteren from the Abbey of Saint Sixtus. Problem is that it is sold exclusively at the abbey, and only after (lucky) reservation (very limited supply), and you must make the promise to the monks not to resell it (no joke). Just have fun reading the link; note the ‘beer phone number’ and ‘ beer phone operator’. I just love Belgians for this…. But hey: a crate of 12 bottles for 30 euros, for the best Trappist in the world, non-commercial, one got to do something for it…. And of course drinking one at the pub in front of the Abbey…. I hope I can still make a reservation at short notice.

Stay purist! Makes life worth living.

cheers,
Ozzy

oldgringo · Jul 18, 2011

Slightly off topic

Oilmaster said:
Thanks for the wiki link on the Black Country, because I was wondering for some time what it was about: "in the 19th century this area had become one of the most intensely industrialised in the nation. The South Staffordshire coal mines, the coal coking operations, and the iron foundries and steel mills that used the local coal to fire their furnaces, produced a level of air pollution that had few equals anywhere in the world. It is popularly believed that the area got its name because of pollution from these heavy industries that covered the area in black soot". Apparently some beer too…
Also, would it be linked to the fabulous rock group Black Country Communion (with Joe Bonamassa and Jason Bonham)

"In 1862, Elihu Burritt, the American Consul in Birmingham, described the region as "black by day and red by night", because of the smoke and grime generated by the intense manufacturing activity and the glow from furnaces at night."
It's where I come from [og]!
[let's see if I can still represent the accent, here] "We da(y) [didn't] si the sun fer tew 'undred year" [lol

]
As for the beer, "A workin' mon by a fernis, would have 'foive' [proper pints] with 'is 'dinner' [lunch!] - 'an a good fifti percent on em, would be in bad sherp [shape] when they got um [home] for theyer tay [supper]. "Yo 'av ta wash the dert dowen wi' summat [something], do(e) ya?" An' they da(y) live all that long either!

I don't know if he came from there but John Bonham certainly had a flat in Dudley in the 60's - a mate of mine went round there for a 'cuppa-tea', more than once. Note the 'Black Country Woman' track on 'Physical Graffiti'! Yes, 'BCC' is doing just great!

Cheers, 'Derve' [

] :thmbsp:

oldgringo · Jul 19, 2011

Back 'on-topic'

Oilmaster said:
Actually, I was thinking about if you could do that rebuilding with glue . . .
Indeed, the shaft measures 9.0 mm (M9 fine thread), and several other sockets I have are all larger . . .
In case the current solution doesn’t hold, and you have a close-matching one, then you could always enlarge the hole in the chassis by filing or drilling. Eventually, I could send you mine.

Thanks again, Ozzy! I was shying away from drilling through the relatively thin plate of the chasis ['teeth-rattling' for the little fella]; but, yes, it might come to that. I'll keep my fingers crossed for the current 'repair' effort; and definitely continue searching.
Cheers, Dave :thmbsp:

Oilmaster · Jul 19, 2011

oldgringo said:
"A workin' mon by a fernis, would have 'foive' [proper pints] with 'is 'dinner' [lunch!] - 'an a good fifti percent on em, would be in bad sherp [shape] when they got um [home] for theyer tay [supper]. "Yo 'av ta wash the dert dowen wi' summat [something], do(e) ya?" An' they da(y) live all that long either!

A believe still held high by many Brits as we see it...

Would be a good footer

oldgringo said:
I don't know if he came from there but John Bonham certainly had a flat in Dudley in the 60's - a mate of mine went round there for a 'cuppa-tea', more than once. Note the 'Black Country Woman' track on 'Physical Graffiti'! Yes, 'BCC' is doing just great! [] :thmbsp:

Well, if Jason's father had a flat over there, and considering the (great) album artwork of BCC, the they must have some roots/base over there, I would say. PS: I start understanding your avatar now.

Ok, let's talk (semi) topic: now that you have a KA-4002A unit, thou ought to have the tuner that came with it: the KT-2001A. I happen to have a second one, which had an unfortunate incident during shipping: the dial glass wash smashed as the tuning knob got a push from the outer world. The chassis holding the dial knob got a bit deformed as well, but I managed to get that back into original position/condition. Fortunately, the dial glass has no printing on it, it only has a certain dark tint. If you are interested, then I can put up a picture here showing the unit/damage.

cheers,
time for a malt,
ozzy

Trio KA-4002a - Now arrived/needing help

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