FDP Home Page / FDP Forum / Classifieds / FAQ's / Links / Cookbook

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.

Acme Guitar Works	Amazon	Antique Electronics Supply	Berklee Music
Bill and Becky Lawrence	Graph Tech Guitar Labs	Guitar Center	Guitar Parts Resource
Guitar Stop	Ludlow Guitars	Music Power	Music123.com
Musician's Friend	The Music Zoo	WD Music Products

* 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 Registered Members: 62,000+ LOST YOUR PASSWORD? ......................................................................

	For Sale/Wanted Classifieds
FDP Jam Calendar		Find musicians in your area!
	Search the Forums

FDP Forum / Amp Mods, Repairs, and Projects / HRDlx with EL34's

Next 20 Messages

rwaterspf1 Contributing Member North Carolina, USA It's all about the tone!	Jan 12th, 2003 06:54 AM   Edit   Profile   Print Topic   Search Topic Anyone tried this? I know it is technically possible to do with just changing the screen grid resistors to 1K/5W and jumping pins 1 & 8 on the powertube sockets, but can the HRDlx tranny handle the increase in heater current or do y'all think it will do a meltdown pretty quickly?
Garage_Studios Richmond, Ky	Jan 12th, 2003 07:45 AM   Edit   Profile   Print Topic   Search Topic There's a fellow on here named Rob Worrall that did this, but he used yellow jackets so he wouldn't have to mod the circuit. He's basically done all the HRD mods you can think of.
nonsqtr usa ...whatever remains must be the truth...	Jan 12th, 2003 08:26 AM   Edit   Profile   Print Topic   Search Topic I have the same question about my Bassman. Where can we get the ratings for some of these Fender transformers?
Steve Dallman Contributing Member USA I met my Tiffany on FDP ! Love exists!	Jan 12th, 2003 09:31 AM   Edit   Profile   Print Topic   Search Topic I don't know if a HRD could take the extra current demands, but here's how you test it. Do the changes. (After the changes, the amp will take 6L6's just fine so nothing is lost.) Measure the heater voltage. It should be 6.3vac. Put in the EL34's. Measure again. If there is a significant drop, maybe below 6.2, it won't handle it. You could always add an auxillary 6.3 volt heater transformer and separate the preamp and power tubes.
Rob Worrall Brisbane Australia	Jan 13th, 2003 06:50 AM   Edit   Profile   Print Topic   Search Topic Well, no, not quite. All I've done is what many HRD owners have done, that is to pop in a set of THD YellowJacket adaptors and use EL84s (not EL34s). The EL84s did lower the volume a bit (maybe 60-70%??) but it was still quite loud enough at sweetspot practice and gig volumes. An attenuator or volbox is still the go for home practice. The YJs came with a pair of JJ EL84s which sound great, but were a bit sharp and shrill for my personal liking (for fat thick rock lava). I popped in my Mullard EL84s and it was like night and day. The Mullards are just rockin' balltearers! Cworr. Now that this topic has been raised, I must certainly discuss the EL34 conversion with my trusty amp tech, B.J. Aaah, why not?! I reckon it would sound immense - provided the amp could take it. Rock on, all good bretheren. (This message was last edited by Rob Worrall at 03:18 PM, Jan 15th, 2003)
rwaterspf1 Contributing Member North Carolina, USA It's all about the tone!	Jan 13th, 2003 04:29 PM   Edit   Profile   Print Topic   Search Topic I ordered the resistors today, should be in by the end of the week. I'll just "borrow" some el34's out of my mesa to try out and see what the voltage drop on the tranny is. I'll post again and let y'all know how it went *edit* I did some checking and the HRD don't fire up the high power caps to feed the plates in "standby" but it does run the heaters..so for fun, with no mods I measured AC voltage from pin2 to pin7 and get 6.89vac with my Philips 6L6WGB's. I plugged in a pair of Svetlana el34's from my mesa and turned the amp power on, and left it in standby. did the same voltage measurement and get 6.72vac. Looks OK or is there a flaw in my testing/theory here? (This message was last edited by rwaterspf1 at 05:44 PM, Jan 13th, 2003)
Garage_Studios Richmond, Ky	Jan 14th, 2003 06:59 AM   Edit   Profile   Print Topic   Search Topic When you find out for sure, please post. I'd love to add this mod to my page. (This message was last edited by Garage_Studios at 07:02 AM, Jan 14th, 2003)
rwaterspf1 Contributing Member North Carolina, USA It's all about the tone!	Jan 16th, 2003 05:23 PM   Edit   Profile   Print Topic   Search Topic got my stuff, made my mods, heres the scoop: replaced both screen resistors (original 470ohm/1W) to 1k/5W and jumped pins 1 & 8 on both powertube sockets. Installed my Philips 6L6WGB's and checked it out. Heaters running 6.56vac at both powertubes, plate voltage 427, grid current 34mA. Installed a pair of JJ el34's and get heaters running 6.48vac, plate voltage 430, and the bias pot maxed out it only draws 16mA. So maxed out it runs *almost* 7W per tube doh! Open to suggestions, looks like I need to make some changes in my bias supply to get the proper wattage out of this tube.
Steve Dallman Contributing Member USA I met my Tiffany on FDP ! Love exists!	Jan 17th, 2003 09:40 AM   Edit   Profile   Print Topic   Search Topic It should be a simple resistor change there also.
Reeko USA	Jan 17th, 2003 10:50 AM   Edit   Profile   Print Topic   Search Topic I am very interested in this mod. Can't wait to hear how it sounds. Steve, I know that once this mod is done, you can still run 6L6 or EL34s. My question is, will the 6L6 sound still be the same? No effect. This would make me more inclined to try.
rwaterspf1 Contributing Member North Carolina, USA It's all about the tone!	Jan 17th, 2003 06:45 PM   Edit   Profile   Print Topic   Search Topic After some trial & error in the bias supply resistance I have found that I am going to rat shack to see if I can get a second pot to put in place of a bias resistor. As it stands now there is no "best of both worlds" with a regular resistor. I got my el34's biased at 35.2mA with 418vdc on the plates and the bias pot all the way up (14.71W) that is in the range at least but a little cold still. Popped in my 6L6WGB's and turn the bias pot all the way down and get 411vdc on the plates and 38.3mA of current (15.74W). Should be ok for 6L6GC's and maybe slightly warm for the 6L6WGB's. Kept in the el84's and played for about half hour with no problems whatsoever, now I'm taking a break :) I can get the el34's biased in the 17W range with one resistor, but the 6L6's were pushing close to 20W, yowza!
rwaterspf1 Contributing Member North Carolina, USA It's all about the tone!	Jan 18th, 2003 12:03 PM   Edit   Profile   Print Topic   Search Topic I found it easier to just install a bias select switch (ala Mesa) to switch between different bias voltages. Now I have a greater range of adjustment for both tube types. I am taking it for a gig this afternoon so I'll see how it holds up with the el34's. Wish me luck!
rwaterspf1 Contributing Member North Carolina, USA It's all about the tone!	Jan 19th, 2003 10:22 AM   Edit   Profile   Print Topic   Search Topic the amp is doing pretty well so far. it has been to 2 practice sessions and one gig and played around the house all weekend and no signs of overheating. I installed my bias switch in the hole where the mains fuse holder was at so now swapping tubes is easy, just don't forget to flip the switch when I put a set of 6L6's in or they won't last long. As far as sound.....the bass is less "punchy" and smoother than with the 6L6's, also the whole amp has taken a little darker tone. I like the sound difference. it went from SRV type twang tones to more of a mesa style clean, the gain channels smoothed out a little as well. push the volume up to 6 or 7 and this baby just sings! thanks for all the help and suggestions!
Reeko USA	Jan 20th, 2003 10:18 AM   Edit   Profile   Print Topic   Search Topic COuld you post the exact mods you made, what resisters you changed etc and where it was best to place the mods. I would like to try this mod.
rwaterspf1 Contributing Member North Carolina, USA It's all about the tone!	Jan 20th, 2003 05:07 PM   Edit   Profile   Print Topic   Search Topic I still don't know what the HRDlx power tranny is rated for, so don't blame me if you blow your amp up :). Also the resistor values shown work in MY amp with MY tubes, you may have to change these slightly for your needs. As in all things electrical, safety first. Make sure your caps are discharged and your amp is unplugged! First off, take a piece of wire (resistor leg, or whatever) and solder pins 1 & 8 together at both power tube sockets. I did this at the top of the PCB where the pins were soldered in. Replace the 470ohm/1W screen resistors to 1k/5W (R61 & R62 in the schem I have). Put in your EL34's and power up..you will be running very low output power at this point but let the amp warm up a little and check the heater voltage between pins 2 & 7 of the power tubes, if you get below 6.3vac, stop now and put your 6L6's back in. My readings were 6.48vac, yours may differ. Unplug, discharge, etc. Now if you plan to run ONLY el34's the next step is your last. the value I used as a bias resistor is 39k/1W. Put your bias resistor in R76. Power switch on, amp in standby, measure voltage at the right side of the bias pot (as looking at it from the rear of the open amp) and check the voltage, in the -35vdc to -40vdc range? fire up the amp and check the plate voltage and grid current. If you are running over 20Watts at idle..crank it down or find a lower value resitor (ie: 22k or 33k). With the 39k my amp runs 418vdc on the plates with a current of 35mA (pot half way up) 418vdc x .035A = 14.63W per tube at idle. This bias will be TOO HOT for 6L6's! I put in a pair to check and it was running in the 45.5mA range with 411vdc on the plates (18.7W) with the pot all the way down. If you want to switch between 6L6's and el34's, I ran a switch on mine. I put a switch and a 1.5k resistor in parallel with the 39k bias resistor. (flip switch "on", close circuit, electricity goes the path of least resistance ..the 1.5k instead of the 39k) Now the amp's bias circuit is "stock". I used 1/2 of a DPDT switch and mounted it in the hole where the mains fuseholder was at (i put the fuseholder inside and zip-tied it to the harness). I'll use the other side of the switch to run coloured LED's to show me what I'm set on. Thinking about getting a big dual LED that fits in the pilot lamp hole red..el34's, green 6L6. (and i get to save the 150mA the pilot draws off my heater circuit!). Again, I take no responsibility for you trying this mod on your amp, i just provide information that is currently working on my own amp (for how long it will work...? lol). If I ever get specs for the tranny I'll post them here, with this mod I should be pulling about 4A out of that heater winding
Rob Worrall Brisbane Australia	Feb 16th, 2003 01:27 AM   Edit   Profile   Print Topic   Search Topic How are those EL34s shaping up in the HRD? Nothing fried yet? How's it sound? Anyone else tried this with success? Cheers Chums
rwaterspf1 Contributing Member North Carolina, USA It's all about the tone!	Feb 16th, 2003 10:26 AM   Edit   Profile   Print Topic   Search Topic The HRDx is still going with the EL34's and nothing has fried yet! As far as sound goes....the bass is less punchy and the highs sing pretty well. If I can talk my better half into using her PC I'll make some mp3's this afternoon
rwaterspf1 Contributing Member North Carolina, USA It's all about the tone!	Feb 16th, 2003 11:25 AM   Edit   Profile   Print Topic   Search Topic first off, no making fun of my playing! hehe volume 3 drive 7 treble 8 bass 3 middle 4 master 2.5 reverb 3 presence 7 guitar stock Guild Bluesbird no effects V1 Telefunken 12AX7 V2 Mullard CV4004 V3 RCA 12AT7 Powertubes JJ EL34 Speaker Weber Ceramic Silverbell Sorry for the quality, it was done in CoolEdit Pro with a PC mic in front of the HRDx MP3 of my HRDx
Garage_Studios Richmond, Ky HRDx - A Modern Day Classic	Feb 17th, 2003 04:04 PM   Edit   Profile   Print Topic   Search Topic Sounds like the mic has too much gain, which is causing a gritty distortion. Double click on the volume control icon that's by the clock (the loudspeaker).. click options from the menu, then properties.. select "Recording", push OK.. turn down the volume of the Mic In (or Line In, whatever you're recording with). You'll be able to tell because its box will be checked. Click "Advanced" and make sure "Microphone Boost" isn't selected. Press OK and exit everything.
rwaterspf1 Contributing Member North Carolina, USA It's all about the tone!	Feb 17th, 2003 05:46 PM   Edit   Profile   Print Topic   Search Topic ahh, thx Garage, turned off the mic boost and tried again, same settings as before on the amp. See if this one is any better MP3

Next 20 Messages

FDP Forum / Amp Mods, Repairs, and Projects / HRDlx with EL34's

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

Moderators: amcrory  Black Hole Gang  Chris Greene  EA6B  Iron Man  Leftee  Lesterstrat  reverendrob  

---

Copyright © 1999-2010 Fender Discussion Page, LLC   All Rights Reserved