KLP1 and K5581 Has a Speaker Channel Down

[JohnG]

I,m so rusty when it comes to thinking about the basic investigations to identify a cause of the loss of the Speaker channel.
I have just set up the KLP1 and K5881, for the first time in a very long time.
I have little confidence in believing my swapping cables is showing the cause of the lost channel.
Could a kindness be offered in supplying a sequence of tests that would help isolate the failing component.
I am not a multimeter/soldering iron using type of person, so I am hoping to be able to identify the component in need of a visit to a local cleverer person than I
Looking forward to kicking myself, when I start recalling some of the advice offered.

[JohnG]

I,ve just plugged the CD Directly into the Power Amp, and both speakers are functioning fine.
I,ve checked every source and only one channel is operating.
I am based near Mildenhall Suffolk,
Is there anybody in the Suffolk/Norfolk/Cambs region who could have a look at a repair on the Pre Amp for me.

[Richard]

Hi John,

Suspect a dry solder joint or disconnected wire, a bad interconnect cable, a bad switch (try all input positions), or a bad valve;

swap interconnects across channels,

clean the valve pins and swap the valves between channels to see if the fault follows or not.

Have a good look around for any disconnected wires and generally compare the good channel with the faulty one on all inputs

[JohnG]

Thank you richard, I will begin to familiarise myself with these actions.

[bob orbell]

Hi John, if you can't sort it, you are welcome to pack and post it to me for repair, there will be no charge to you, except any parts and return postage, I am in Kettering Northants. BOB

[JohnG]

Thank You Bob
Your offer is very kind and I may have to take you up on it.
I will see my movements over the next few weekends, and see if I can avoid the Posting of the Package.

[JohnG]

I have been doing my very inexperienced investigations as advised.
Swapped out interconnect cables, Checked all source inputs, give valves a wriggle in their sockets, re-positioned valves.
All the above have had no effect on a hum noise and activity from the bass driver on one channel.
Here is a strange finding for me, the hum/bass driver activity is still at the same level when the pre amp is switched on/off, the volume control will work to adjust the volume with the same effect when the pre amp is switched on/off.
When the Pre amp is switched off, music can be heard through the working channel at the speaker at a low volume level.
I will assume this is a seen before experience for some, for me its all X Files stuff.

[Richard]

Hi John,

Good work so far. Yes there will still be music and the volume pot will still vary the level even with the pre switched off. The pre is a simple cathode follower and there is a continuous AC connection through it which isn't broken by the valve not operating. The signal will be attenuated by about 30dB though so the result will be as you describe.

You say the power amp works on both channels but we need to know the source of the hum and establish if the pre is faulty;

1) Connect the CD player, switched off, to the power amp without the pre. Switch on just the power amp and listen for noise at both speakers. Expect some hiss and a little hum but check it is at a similar low level from both. If one channel noise is noticably louder then there is a power amp fault.

2) If the speakers are similar (suggesting the power amp is ok) connect the pre to power and the CD player to the pre. With the CDp and pre off, and the power amp on, listen again at the speakers. The hiss and hum should be at a similar low level on both.

3) With the CDp still off, turn on the pre and listen again. If the noise is not still similar on both something in the pre is causing it.

Try to report your findings for each of these 3 connections and it should tell us where the problem lies.

[JohnG]

Hi Richard
Thank you for your directions, I have followed your last three tasks and I now have my KLP1 working on both channels with the K5881.
At each task, I had a very low background hum at a very similar audible level at each speaker.
I then turned on the CD Player and there was not any interference seen or heard. Bob Marley is now filling the house
After getting up close to the Speakers, I have just noticed that one of my
HD-3P Golds has lost a little air from the Easter 2017 DIY recharge.

I have researched the methods used, as a result, I am looking to make a recharging device for this with a controlled Atmospheric Pressure inside. I now have two pairs of these HD-3P's so will try a few different HPa charges.
I have read 1015 HPa is a good one to the ear
The real plus point is I can get my original ESL 57's up and running, and carry out A/B comparisons to my recently purchased One Thing Audio overhauled pair.
As I have been using a 50% complete monoblock 845 with shared speaker terminals and a Y connector for the RCA Interconnects, the 1-2 Ohm impedance that could have been created with ESL/50% complete amp could have damaged the expensive amp, so the A/B comparisons was on hold.
Your help has now allowed me to commence with my investigations into how my Stacked Quads will be produced in relation to Bass/Treble Panels.

On another note, I have visited shows and listened to many speakers this year, DIY Projects, OB's, to very expensive commercial models, I purchased the KLS3 Gold Dome for £170, they are a variation in cabinet, as it is five sided and has a external crossover, in my mind and recollection of other reproductions heard this year, it is a extremely competent speaker, and have proved amazing value for money.