It is currently Tue Mar 17, 2020 3:11 am

All times are UTC - 7 hours



Post new topic Reply to topic  [ 23 posts ]  Go to page Previous  1, 2
Go to page Previous  1, 2
Author Message
Post subject:
Posted: Fri Jun 04, 2010 5:11 am
Offline
Rock Star
Rock Star
User avatar

Joined: Tue Aug 07, 2007 2:19 pm
Posts: 8827
stratele52 wrote:
GLjazz, You are better to find a good tech ( not anybody in music store) to do a good bias to your amp.

Right now in this forum, to much incomplete or wrong informations to help you .

Don't forget , there are some very dangerous voltage in tubes amp it can kill you.


I agree to a point. Yes there are lethal voltages but there's not that much misinformation. I linked the OP to a biasing video from a guy who is a qualified amp tech as well as a JJ/Tesla distributor. The really huge misinformation here is confusing mV and mA. I doubt you could even bias the amp at 60ma. Sometimes it won't even go as high as 40mA it depends on where the component tolerances actually are. My HRDlx could barely make it to 90mV. The only reason I wouldn't go higher than 85mV is because I didn't like how early the amp broke up biased that hot.

_________________
Life...... It's sexually transmitted and always fatal


Top
Profile
Fender Play Winter Sale 2020
Post subject:
Posted: Fri Jun 04, 2010 8:48 am
Offline
Hobbyist
Hobbyist

Joined: Thu Mar 11, 2010 7:29 pm
Posts: 14
Alright, now we're getting somewhere. I popped in the new tubes, biased properly to 60mV as per Supro's video and the eurotubes video for HRDlx, and they are both glowing happily.

However, after sitting and listening and looking for about half an hour i believe i have tracked the source of the hum to the hole in the PCB that leads to the output transformer...

And what causes problems with the OT? Improper speaker load.... It appears fender cheaped out on the wiring and somewhere in the rats nest of tied wires they left there is a break. Resistance check revealed all kinds of crazy values. Next step was to run the speaker out to half of my 1960A Cab. Sounded MUCH better, but the lows were still a bit muddy especially in chords, and every once in a while it would sound like it was losing a bit of power to the speakers and regaining.

Oddly, the main fuse was not blown or hot, etc. Could this humming be an overheated and permanently damaged OT? If so, would that cause muddy lows yet preserve highs?

And more importantly... if its the OT, is it worth shelling out the cash to repair? Thanks a ton for your help so far!

Gracias,
David


Top
Profile
Post subject:
Posted: Fri Jun 04, 2010 8:56 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
The "iron" in the HR-series is actually pretty good -- I think it'd be somewhat unusual to see a damaged O/T (usually they short to ground then burn "open" altogether).

Take a look at the HV components in your P/S. The "sag" you mentioned may be the result of some wonky diodes.

HTH

Arjay


Top
Profile
Post subject:
Posted: Fri Jun 04, 2010 9:31 am
Offline
Rock Star
Rock Star
User avatar

Joined: Tue Aug 07, 2007 2:19 pm
Posts: 8827
GL 60mV IMO is really cold.

_________________
Life...... It's sexually transmitted and always fatal


Top
Profile
Post subject:
Posted: Fri Jun 04, 2010 2:00 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Sat May 08, 2010 4:31 am
Posts: 411
Location: France
Stratele52,

No confusion, I was thinking 6L6GC for HR ...

Tissan


Top
Profile
Post subject:
Posted: Sat Jun 05, 2010 8:30 am
Offline
Hobbyist
Hobbyist

Joined: Thu Mar 11, 2010 7:29 pm
Posts: 14
Retroverbial- Thanks for the input that's definitely a comfort.

I've been doing electronics stuff for a long time now but the troubleshooting individual components in the amp is more foreign to me. Is there any way to visually spot a bad diode?

Any ideas at all? I'm getting ready to take it to a tech if I can't figure out exactly what is causing this. I rewired the speakers with good quality speaker wire but something is still causing TERRIBLE sound quality. Single notes are okay, but any kind of chord turns in to headache creating mud.
Sounds like all the speakers are blown, or made out of plastic cups, or something. (I did test them, its not the speakers.)

Should i just bite the bullet and take it in? What should i expect to pay if i do, if you guys have any experience in that department?

Thanks to all for the input on the bias... i did bring it up to 68 mA, and yes, it still sounds awful.


Top
Profile
Post subject:
Posted: Sat Jun 05, 2010 10:11 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
At this point I'd say it's time to let somebody with "cred" take a look at it. Find yourself a good tech and explain the symtoms. Expect to pay at least $30/hr plus whatever parts are needed.

If you're "joined at the hip" with this amp, keep his number on speed-dial.

Good luck

Arjay


Top
Profile
Post subject:
Posted: Sat Jun 05, 2010 4:01 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Tue Aug 07, 2007 2:19 pm
Posts: 8827
Retroverbial wrote:
At this point I'd say it's time to let somebody with "cred" take a look at it. Find yourself a good tech and explain the symtoms. Expect to pay at least $30/hr plus whatever parts are needed.

If you're "joined at the hip" with this amp, keep his number on speed-dial.

Good luck

Arjay


+2 My tech was on a retainer with my HRDlx LOL.

_________________
Life...... It's sexually transmitted and always fatal


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 23 posts ]  Go to page Previous  1, 2
Go to page Previous  1, 2

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: