Author Topic: one woofer pump_ground issue?  (Read 5261 times)

Offline data

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one woofer pump_ground issue?
« on: October 07, 2014, 01:16:39 AM »
Hay guys

I'm at a lose on this one  :(

With the EAR Clone I have a touch of hum, slightly more in the right.

But the issue I'm trying to sort out (might be one and the same) is that when adjusting the volume pot on my main amp, the right speaker woofer pumps (left does not). There is a whooshing sound with it, move the volume up and pushes the cone outwards and move it down and it sucks it inwards. This only happens with the movement of the volume pot.

I think It's a grounding issue of the Clone as a CD played is OK, but wondering if the above symptom can narrow it down in any way?

The IEC earth goes to the ground post for the tables lead on the inside of the case, and this is the chassis ground point. I have tried it with the circuit ground (from PCB) tied directly from the RCA grounds to this point with and without a cap, and floating also, doesn't make any difference. table ground wire connected and not, still no difference.

Any ideas?

Thanks
Ian

Offline klackto

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Re: one woofer pump_ground issue?
« Reply #1 on: October 07, 2014, 07:57:36 AM »
Sounds like there may be DC on the output of the pre. One of the coupling caps may be leaky.

Offline data

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Re: one woofer pump_ground issue?
« Reply #2 on: October 07, 2014, 01:29:30 PM »
That would be a VSF cap :(

I'll swap them over and see what happens.

Cheers

Offline Tuyen

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Re: one woofer pump_ground issue?
« Reply #3 on: October 07, 2014, 01:40:03 PM »
Does sound like a leaky output cap.

Fingers crossed it isn't a vsf.  In saying that, I've had two vsfs fail in the past. So I wouldn't be surprised.

Let us know how you go :)

Offline stevenvalve

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Re: one woofer pump_ground issue?
« Reply #4 on: October 07, 2014, 01:46:14 PM »
Does sound like a leaky output cap.

Fingers crossed it isn't a vsf.  In saying that, I've had two vsfs fail in the past. So I wouldn't be surprised.

Let us know how you go :)
I to have had some fail, an expensive problem

Offline data

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Re: one woofer pump_ground issue?
« Reply #5 on: October 07, 2014, 02:05:53 PM »
I'm not really surprised that I didn't (want), to consider it, but with no input caps on the amp, and only the VSFs on the output of the phono..... *sigh*

Will check them shortly, need to wake up fully first......yeah I know It's 1pm :)

Offline data

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Re: one woofer pump_ground issue?
« Reply #6 on: October 07, 2014, 02:38:11 PM »
Doh!

Swapped the VSFs over for a pair of Dayton caps..........now It's on the other channel only  ::)

Edit: The VSFs test OK for capacitance measured out of circuit, but how the hell did it swap from one channel to the other with the caps change.......weird!
« Last Edit: October 07, 2014, 02:47:54 PM by data »

Offline data

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Re: one woofer pump_ground issue?
« Reply #7 on: October 07, 2014, 04:50:51 PM »
The very good thing about this...

Is I found it before trying any of Steve's Red base lovely's in it :)

Offline data

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Re: one woofer pump_ground issue?
« Reply #8 on: October 07, 2014, 05:17:56 PM »
My bad!

Showing my lack of knowledge again.

Pulling the valves is not what I should have done as I'll get peak voltages, and heaters are fine as being shared across the two of each valve means one is positive and one negative....nothing hurt luckily ;)

OK, so I'm back to this  pumping woofer again, so a grounding issue maybe.

I'll check the table, but as it changed from one channel to the other with the cap change I don't think so.

Edit: Going back to a cheap old CD player until I work this out :(
« Last Edit: October 07, 2014, 06:23:22 PM by data »

Offline data

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Re: one woofer pump_ground issue?
« Reply #9 on: October 07, 2014, 09:27:57 PM »
OK, have reworked the connections for the musicaps, remounted the VSFs, and replaced the heater wires as they looked messy anyway.

The only thing I can think of that could have changed when the pumping changed to the other channel is the remounting of the RCA sockets. So making double sure that they are definitely isolated from chassis.

Fingers crossed

Oh, I confused myself (as I can do) about the heaters, they must be in parallel not series.

Offline data

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Re: one woofer pump_ground issue?
« Reply #10 on: October 07, 2014, 09:37:49 PM »
It's still there, and back in the original channel.

Meh.....

Back to the sweeter sounds of the phono. I'll need to redo the phono section point to point in the future, seems to be something up with how it is now but I can't see the cause of that strange woofer/volume adjust thing. At least there is nothing amiss with the sound or the drivers outside of this.
« Last Edit: October 07, 2014, 10:13:31 PM by data »

Offline kajak12

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Re: one woofer pump_ground issue?
« Reply #11 on: October 08, 2014, 11:00:27 PM »
It's still there, and back in the original channel.

Meh.....

Back to the sweeter sounds of the phono. I'll need to redo the phono section point to point in the future, seems to be something up with how it is now but I can't see the cause of that strange woofer/volume adjust thing. At least there is nothing amiss with the sound or the drivers outside of this.
Just get digital you have less problems
still discovering the link between electronics and audio reproduction.so much to learn and so little time

Offline data

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Re: one woofer pump_ground issue?
« Reply #12 on: October 09, 2014, 01:10:10 AM »
Just get digital you have less problems
Mario..... not going to help, as the stylus will just slid all over those little shinny drink coasters ;)

The problem here isn't the turntable, It's a tube phono, maybe I should go SS instead?
 :D
« Last Edit: October 09, 2014, 03:36:24 AM by data »

Offline data

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Re: one woofer pump_ground issue?
« Reply #13 on: October 10, 2014, 12:39:00 PM »
Eek!

Just measured for DC on the output RCAs of the phono stage, .65vdc on one and 45vdc on the other  :o

Something very odd here!

Offline Tuyen

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Re: one woofer pump_ground issue?
« Reply #14 on: October 10, 2014, 12:51:22 PM »
The output cap is not doing its job! :o

Offline data

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Re: one woofer pump_ground issue?
« Reply #15 on: October 10, 2014, 12:55:54 PM »
It's strange though as when I pulled the VSF they measure correct in capacitance and when subbed with some Dayton's that high DC moved to the other channel.

Needless to say, i won't be using the pbono stage until I nut this out.............the nut possibly being me  :D

Offline data

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Re: one woofer pump_ground issue?
« Reply #16 on: October 10, 2014, 12:58:37 PM »
I may need to order some new (not Duelund) output caps.

But I'll have yet another good look over the PCB  ::)

Have a couple of pairs of Russian PIOs here suitable, so will replace the VSFs with those and see what I read.
« Last Edit: October 10, 2014, 01:04:00 PM by data »

Offline data

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Re: one woofer pump_ground issue?
« Reply #17 on: October 10, 2014, 01:55:16 PM »
OK, with the PIOs in place while the reading is a little erratic, one reads between 25mv to 35mv and the other between 2mv/3mv and 15mv

The Duelunds were mounted underneath the PCB while these are mounted on top, I guess that has no bearing on the readings, does this mean the VSF's are stuffed?

OK, no strange woofer action when adjusting the volume now, but DAMN! Russian PIOs are no substitute for VSFs  :'(

Edit: hmm...I'm still wondering if the issue was mounting the caps on the underside of the PCB  :-\
Edit part 2: I'm near certain that it was the mounting on the underside that was the issue (nothing else makes sense to me), picking up interference, but no where else to mount the VSFs. The PIOs are OK but a definite step back. looks like I need to rebuild this thing soonish, that way I can construct it point to point while at it.
« Last Edit: October 10, 2014, 10:25:41 PM by data »

Offline data

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Re: one woofer pump_ground issue?
« Reply #18 on: October 11, 2014, 11:43:43 PM »
OK, I tried mounting the VSF off to the side & shielded with mu-metal, with leads running a short distance across the upper PCB and no go. Again over half a volt on one and 46v on the other.

Damn!
I might wait a bit and see the comparisons with the Jupiters before replacing the Russian PIOs, don't like the PIOs but not willing to risk Duelunds again.

Drove down for some smokes just before, and took the VSFs with me and tossed them in the dumpster. Was going to go into the bins downstairs, but I know myself and would have obsessed on them and fished them out in more fruitless attempts to use them  ::)
« Last Edit: October 12, 2014, 01:34:22 AM by data »

Offline stevenvalve

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Re: one woofer pump_ground issue?
« Reply #19 on: October 12, 2014, 02:10:47 PM »
Don't throw them away, you can use them in a crossover and other applications, in a crossover they work in a different way, and will work perfectly. I had some faulty one's. they had AC on the output but in my crossover they worked fine.
« Last Edit: October 12, 2014, 02:15:27 PM by stevenvalve »