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Post subject: HRD: Loud noises in the morning
Posted: Thu Feb 04, 2016 7:15 am
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I know that tubes are the usual suspects but given that I've changed preamp tubes and recently changed the power tubes in my almost 4-year old HRD, I'm thinking this may be an indication of a more serious issue.

Over the last week or so it's happened a few times that there are loud crackling and sizzling noises after the amp is on for a few seconds. This continues for no more than 30 seconds and the noises are present when playing, not playing, and even when a cable is not plugged in to the amp. After 30 seconds everything returns to normal.

Any ideas as to what could be causing such behaviour?

Thanks and Cheers!
BM

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Post subject: Re: HRD: Loud noises in the morning
Posted: Thu Feb 04, 2016 8:19 am
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At 4 years old, if its been heavily used, it could be ready for a resolder job on the PCB and tube boards.
When it sizzles, give it a sharp rap with your knuckles on the rear cover, just above the lower center cover screw.
If that affects the sizzle, there's a couple resistors that need resoldering that are right under that screw.


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Post subject: Re: HRD: Loud noises in the morning
Posted: Thu Feb 04, 2016 10:04 am
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TimsAudio wrote:
At 4 years old, if its been heavily used, it could be ready for a resolder job on the PCB and tube boards.
When it sizzles, give it a sharp rap with your knuckles on the rear cover, just above the lower center cover screw.
If that affects the sizzle, there's a couple resistors that need resoldering that are right under that screw.


+1

That'd be my guess as well.

Arjay

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Post subject: Re: HRD: Loud noises in the morning
Posted: Thu Feb 04, 2016 1:40 pm
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Thanks for the replies. As always, very much appreciated.

Is this something covered by the warranty? Can a qualified tech can see the problem immediately upon opening up the amp or does he need to duplicate the issue in order to proceed? If my previous experience is an indication then the tech will want to duplicate the problem and given that this only happens intermittently and then only over night when the amp has been off for many hours, I'd be without the amp for an extended period which isn't an option.

As for "heavily used" it has been used almost every day and it's also somewhat road worn. but otherwise in great shape.

Cheers!
BM

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Post subject: Re: HRD: Loud noises in the morning
Posted: Thu Feb 04, 2016 1:47 pm
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If the warranty is still valid, the issue is likely covered. And due to the nature of troubleshooting intermittent problems such as yours, you're probably going to be left without the use of the amp for some time.

Arjay

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Post subject: Re: HRD: Loud noises in the morning
Posted: Mon Feb 15, 2016 1:44 pm
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Bluer Monkey wrote:
If my previous experience is an indication then the tech will want to duplicate the problem and given that this only happens intermittently and then only over night when the amp has been off for many hours, I'd be without the amp for an extended period which isn't an option.


Since it's an intermittent problem, any tech worth his salt is going to need to have it on the bench for a while. Both to replicate the problem so he can track it down, and then for a while after he has worked on it to make sure that it's actually fixed.

The only other option is to pay his hourly minimum bench rate to have him randomly resolder some things in the hope that he somehow fixes it. Chances are that you'll have to take it back to him several times using this method, and pay his hourly minimum bench rate each time. By the time you've had it back three or four times, you could have bought a new one!

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Post subject: Re: HRD: Loud noises in the morning
Posted: Mon Feb 15, 2016 3:49 pm
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thompal wrote:
The only other option is to pay his hourly minimum bench rate to have him randomly resolder some things in the hope that he somehow fixes it. Chances are that you'll have to take it back to him several times using this method, and pay his hourly minimum bench rate each time. By the time you've had it back three or four times, you could have bought a new one!


Amps such as those are known as "hangar queens".

:mrgreen:

Arjay

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Post subject: Re: HRD: Loud noises in the morning
Posted: Tue Feb 16, 2016 3:20 am
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Bluer Monkey wrote:
... recently changed the power tubes in my almost 4-year old HRD,

Thanks and Cheers!


BM


Did you check bias ?


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Post subject: Re: HRD: Loud noises in the morning
Posted: Tue Feb 16, 2016 6:37 am
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stratele52 wrote:
Did you check bias ?
Salut stratele52. I didn't check the bias because I replacement power tubes were of identical make and number.

Cheeers!
BM

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Post subject: Re: HRD: Loud noises in the morning
Posted: Tue Feb 16, 2016 6:41 am
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Bluer Monkey wrote:
stratele52 wrote:
Did you check bias ?
Salut stratele52. I didn't check the bias because I replacement power tubes were of identical make and number.

Cheeers!
BM


Groove tubes ?

I alway check bias with new tubes , if tube are the right one ( need no bias ) this do not tell if bias circuit work well, if tubes / pins contacts are ok , if tubes are good and matched ( yes it should be . ) and more...


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Post subject: Re: HRD: Loud noises in the morning
Posted: Tue Feb 16, 2016 6:48 am
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Yes. Identical to the stock set I replaced.

Cheers!
BM

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Post subject: Re: HRD: Loud noises in the morning
Posted: Tue Feb 16, 2016 6:57 am
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Bluer Monkey wrote:
Yes. Identical to the stock set I replaced.

Cheers!
BM


Most of the time it is ok. Follow Tim advice. Need some solder job.
After 4 years is there any waranty ?


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Post subject: Re: HRD: Loud noises in the morning
Posted: Tue Feb 16, 2016 9:23 am
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These amps are as common as crows. Most experienced techs know all the usual suspects.
A good resolder job, in my opinion, means every solder joint on the amp. If I'm gonna charge for a job, the difference is about 10-15 minutes.
Before I resolder the amp or disturb it any other way, I probe for intermittents.
First suspect is the Ext Speaker jack. It's easy to chase away this intermittent, or it may not have surfaced yet.
It causes a dropout during loud passages. To chase it down:
With the amp off and the back off, pull the speaker plug out. Install a blind open plug or slide a piece of cardstock between the switch contacts of the Speaker jack.
Now measure the resistance between the green wire of the speaker jack to the green/yellow wire of the Ext speaker jack.
Anything over 1 or 2 ohms indicates a guilty Ext jacj switch.
Apply a sentence of solvent on cardstock to the offending contacts.
Next is to tap tap on the board to track down obvious instabilities. This is done with an audio generator and a scope. I use a Sharpie marker for a tapping tool.
Then I hook up the generator to the scope and apply a 100KHz square wave across the capacitors. A good cap shorts the signal, A bad cap will only alter it.
Only then will I open it up for resolder.
I scrape away the green coating from the traces around the big resistors and zeners. Then I tin them for better heat dissapation.
Then I install a high end chip in the reverb and a 2.2uF in the cathode of V1 if they use a bass player.
Then I douse all the plastic jacks with hot melt glue to stabilize them.
Yea, after 50 or so HRDX, its not random anymore. Its a system.to keep em from becoming hangar queens


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