FDP Home Page / FDP Forum / FAQ's

The FDP is made possible by the following companies and individual members like you.
Please use the links below to show them we value their sponsorship.

WD Music

Sweetwater

Yellowjackets Tube Converters

Amplified Parts

MOD KITS DIY

Musician's Friend

Antique Electronics Supply

Amazon

Jensen Loudspeakers

Guitar Center

Apex Tube Matching


* God bless America and our men and women in uniform *

* Illegitimi non carborundum! *

If you benefit and learn from the FDP and enjoy our site, please help support us and become a Contributing Member or make a Donation today! The FDP counts on YOU to help keep the site going with an annual contribution. It's quick and easy with PayPal. Please do it TODAY!

Chris Greene, Host & Founder

LOST YOUR PASSWORD?

......................................................................

   
FDP Jam
Calendar
Find musicians
in your area!
  Search the Forums  

FDP Forum / Amp Mods, Repairs, and Projects / Hot Rod Deluxe 3 Issues...

OldSaintNick

USA

Nov 28th, 2016 03:27 PM   Edit   Profile   Print Topic   Search Topic

Hello, brand new member Nick here. I've got a HRDx 3 that out of the blue started on the clean channel sounding wooly, slightly distorted, like a blanket is over the amp, clarity gone and dull. First of all, I changed all (power and pre) the tubes..no change. Plugged in a different speaker to the output, sounds the same with any speaker. Plugged my speaker into another amp, my speaker sounds fine. Plugged into the power amp...no change in sound. Biased at 74mv, C31 =415v, C33=414v, C35=368 C36=315

D13, R78 & 79 slight heat discoloration
V4 is WAY hotter than V5

Before I start major surgery...which I don't know where to start any way, I was going to irresponsibly shotgun fix (replace a bunch of stuff and see if its fixed). I was thinking of getting the Fromel mod and HOPEFULLY that would fix it, but thats wishful thinking. I also started thinking about gutting it and doing point to point...very frustrating.

From everything I've read, It looks like I have similar issues except loss of power. It sounds like a dying tube/tubes but unless I used bad tubes when I changed them out twice, I'm not sure about what else to do. Is there anything I can read from my multi meter that would help diagnose before doing anything else? Any and all help appreciated, It's been a month of research before posting and now i;m here...

Steve Dallman
Contributing Member
**********

Merrill, Wisconsin

Age is just a number...mine is big
Nov 28th, 2016 03:49 PM   Edit   Profile   Print Topic   Search Topic

I have worked on a few HRD's that had socket problems and one of the tubes would lose bias.

That tube would get hot, and the amp would still work, but because it would be running on only the other tube it would distort badly and sound awful.

I cleaned and retentioned the sockets, but could never get that one to stay working.

I ended up replacing the sockets in HRD's that had this problem. The last one, I put a different type of socket (ceramic) just to move away from the original type. The others I used OEM types and didn't have them return.

OldSaintNick

USA

Nov 28th, 2016 04:01 PM   Edit   Profile   Print Topic   Search Topic

So is there a way to check that with a meter to see if it's working correctly? Obviously one tube is hotter than the other. Maybe its a cracked trace if you think it's a tube socket issue?

Hammond101
Contributing Member
**********

So. Cal. USA

Nov 28th, 2016 04:42 PM   Edit   Profile   Print Topic   Search Topic

Steve May be correct.

I would first re-float the solder pads at all of the power tube socket pins on the tube board. Cross you fingers if a magnified inspection does not find a broken joint. This has fixed some for me however.

You might want to measure the negative bias voltage at pin 5 of each power tube socket to see if they are equal. If not equal at the solder pad your issue is elsewhere. Then you could just trace back through the circuit for find the problem.

This is a very difficult thing to "meter" as the tube pin may be not making contact with the socket inside hence a loss or partial loss of bias. Stick a meter probe in there and yes you have bias voltage. You might try a socket re-tension explained at the top of this section of the forum.

Since you have tried different tubes with the same result you might try a socket type bias probe. Possibly you may experience the loss then. It's hit and miss.

And still, it may not be a bias issue at all.

I had a bad preamp tube socket in one of my builds a while back. The thing would oscillate and I could not find the source. Finally on day I was probing around trying to change lead dress and it stopped. I could move the wire connected to that pin and all was quiet. Changed the socket and never an issue after.

OldSaintNick

USA

Nov 28th, 2016 08:22 PM   Edit   Profile   Print Topic   Search Topic

Ok...so i was a bad plate load resistor...R62...Changed it and it was working like brand new....Now I forgot to plug in the I believe CP 13 and 14 the two blue wires coming from the transformer that plug into the end of the board near V5 and turned on the amp...now it's distorted and I can only hear it if I turned it up all the way to 12...did I fry something? Tell me it wasn't the transformer...


OldSaintNick

USA

Nov 29th, 2016 02:21 PM   Edit   Profile   Print Topic   Search Topic

What are those wires (p13&14) connected to and what does turning on the amp without them plugged in effect?


Hammond101
Contributing Member
**********

So. Cal. USA

Nov 29th, 2016 02:37 PM   Edit   Profile   Print Topic   Search Topic

Looks like those are the heater wires for the tube filaments.......Ouch. Could have done some tube damage.

I guess it would be possible to short a tube in this cold configuration and damage the output transformer. Fingers crossed?

OldSaintNick

USA

Nov 29th, 2016 02:38 PM   Edit   Profile   Print Topic   Search Topic

Damnit...How do I check that...?


OldSaintNick

USA

Nov 29th, 2016 02:43 PM   Edit   Profile   Print Topic   Search Topic

Tube damage would be much preferred over transformer damage....


OldSaintNick

USA

Nov 29th, 2016 03:55 PM   Edit   Profile   Print Topic   Search Topic

Help?

OldSaintNick

USA

Nov 29th, 2016 06:34 PM   Edit   Profile   Print Topic   Search Topic

Update just tested all the tubes (pre&power) in another amp and they're fine. Ready to check readings from the transformer/s but dont know what i'm looking for or what the readings should be.

Hammond101
Contributing Member
**********

So. Cal. USA

Nov 30th, 2016 09:43 AM   Edit   Profile   Print Topic   Search Topic

My best guess since the tubes work in another amp is the OT is fine but you never know. I think you most likely mucked something else up or/and have wires plugged into the wrong spade, that could be very detrimental to the health of the amplifier. To pull one of those HRD boards to clearance to solder I remember only having to pull two spades from about the middle of the board and cut some zip ties. Hopefully you took some photos of the board and wiring before you started to refer to.

CP13-14 are the heater connections, voltages are shown in the schematic.

All the other voltages are provided in the schematic I provided in your other thread.

There was a comment about the speaker plug being plugged into the wrong jack. Double check this please.

In all honesty if something doesn't jump out at you, best to seek professional help at this time, local tech is advised.

Steve Dallman
Contributing Member
**********

Merrill, Wisconsin

Age is just a number...mine is big
Nov 30th, 2016 10:27 AM   Edit   Profile   Print Topic   Search Topic

The symptoms you described were what a push pull amp single ending sounds like. One tube was shut off.

Glad you found it.

OldSaintNick

USA

Nov 30th, 2016 11:19 AM   Edit   Profile   Print Topic   Search Topic

If only one tube was working then I'm wondering why both tubes would pulse blue when strummed? Definitely not plugged into the wrong speaker jack, although that is a common mistake. I don't need a tech although advice from one wouldn't be a bad idea. I have been repairing, modding and building things since middle school and am determined to do it myself, safely. I figured out what was wrong in the first place so I'm confident I can do this as a tech would be just guessing and measuring like me with more knowledge. However, I'm curious if there is a section, signal path, or specific area other than the tubes and transformer that would be affected if those wires weren't plugged in. I definitely remembered to plug everything in the right spot (although I forgot to plug something in...). I will double and triple check that. Anymore ideas other than and amp tech or check each part methodically cap by cap, diode by diode, etc..?

Hammond101
Contributing Member
**********

So. Cal. USA

Nov 30th, 2016 04:31 PM   Edit   Profile   Print Topic   Search Topic

Since you said you plugged into the power amp and got the same results I would limit my search to the phase inverter and beyond. Just for good measure, if the amp can be run safely, I would try the preamp out into another amp to test it and rule it out. No telling what is going on here.

You might check the websites of after market suppliers of the output trans. They might have test specs or something of value you can measure in your OT. Any OT for a 2-6l6 push pull amp with an 8 ohm output should be close.

That really is all I have to offer and where I would start if the amp were on my bench.

FDP Forum / Amp Mods, Repairs, and Projects / Hot Rod Deluxe 3 Issues...




Reply to this Topic
Display my email address             Lost your password?
Your Message:
Link Address (URL):
Link Title:




Moderators: Chris Greene  Iron Man  reverendrob  

FDP, LLC Privacy Policy: Your real name, username, and email
are held in confidence and not disclosed to any third parties, sold, or
used for anything other than FDP Forum registration unless you specifically authorize disclosure.

Furtkamp.com 
Internet Application Development

Copyright © 1999-2017 Fender Discussion Page, LLC   All Rights Reserved