Problem with my Darling! - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 22nd February 2005, 06:13 AM   #1
diyAudio Member
 
philipbarrett's Avatar
 
Join Date: Feb 2005
Location: Dallas, Texas
Send a message via AIM to philipbarrett
Default Problem with my Darling!

well at least my amplifier Darling! I have recently finished a Darling with the schematics on Bob Danielak's website. This is the first thing I've ever built except for a few headphones amps & such so please excuse any newbie howlers here. The amp is finished but has very low gain (only enough to drive headphones to a moderate level) and I've really run out of ideas.

Here's the facts Ma'am (with a 400Hz test tone from my iPod line out);

1) input to 6J4 = 88mVAC (100K resistor to ground)
2) output from 6j4 (pin 7) = 34VAC
3) input to 1626 (pin 5) = 34VAC
4) output from 1626 = 10.41VAC

yes Virginia it's an attenuator!

Now all my other voltages read correctly, the 6J4s are seing about 160VDC and the 1626s about 248VDC, the heaters read 12VDC across the pins.

These readings are the same for both channels but being a rank newbie I'm reluctant to assume that both tubes are funky. At this point my limited skills and experience are tapped out and I throw this to the group in the hope that someone has seen this before.

Thanks in advance for your time.

Philip
  Reply With Quote
Old 22nd February 2005, 08:59 AM   #2
diyAudio Member
 
Join Date: Feb 2005
Location: Knoxville TN
Philip,

What is the voltage at the cathode of the 1626? Any possibility that the value of the cathode resistor is wrong on both Channels?

Also, tell us if it is a stereo amp or monoblocks.

Cheers/The Fader
  Reply With Quote
Old 22nd February 2005, 09:10 AM   #3
diyAudio Member
 
Join Date: Feb 2005
Location: Knoxville TN
BTW,,congratulations on your first amp and good on ya' that you chose to build SE !!!

You are most probably on a road that you'll sepnd a lifetime travelling. I build my first circuit in 1956, as a Boy Scout "denner" for a Cub Scout den. Believe it or not, in those days, each level of CS Handbooks had an electonic project.

I was tagged to build a one-tube radio as an example to the cubs. A local Radio--TV repair shop provided the parts and allowe me to sit there and build it with lots of help and encouragement from the proprietor. The radio worked just fine after I'd mowed enough lawns to buy the batteries!!!

BTW, the next level of project was a two-tube redio, which I built the next year ann I wound some coils for short-wave (not in the book, these were just guesses as to the turnsm, I had no idea that this could be calculated!!!) and actually heard some hams talking and some morse code. I eventually became a ham radio operator and built all sorts of stuff including transmitters and receivers.

I sincerely hope you enjoy your Darlings after we get you amplifying :-) That's a marvelous amp.

Cheers/Fader
now listening to Willie Nelson, Red Headed Stranger on vinyl; AWESOME!
  Reply With Quote
Old 22nd February 2005, 06:04 PM   #4
diyAudio Member
 
philipbarrett's Avatar
 
Join Date: Feb 2005
Location: Dallas, Texas
Send a message via AIM to philipbarrett
What is the voltage at the cathode of the 1626? Any possibility that the value of the cathode resistor is wrong on both Channels?

Thanks for your help. I'm reading just under 27VDC at the cathode (pin 8) of both 1626s, the cathode resitor (I'm presuming it's the one that ties 8 to ground) is a 500R/5 watt.

The amp is stereo not monobloc.

'Preciate it!

P
  Reply With Quote
Old 22nd February 2005, 06:43 PM   #5
diyAudio Member
 
Join Date: Mar 2004
Location: aberdeen, uk
Send a message via AIM to martinab2 Send a message via MSN to martinab2 Send a message via Yahoo to martinab2
Probably a silly question... but have you checked that the output transformer windings are the right way round? Maybe its only me who would do something silly like getting the input and output mixed up
  Reply With Quote
Old 22nd February 2005, 08:28 PM   #6
diyAudio Member
 
philipbarrett's Avatar
 
Join Date: Feb 2005
Location: Dallas, Texas
Send a message via AIM to philipbarrett
Thanks for the idea. I agree, the transformer looks like a likely suspect. I checked the Hammond specs on the 269EX, primary is blue/brn and secondry (for a 5K prim/8 ohm sec) is black/yellow which is as I wired it. but maybe I'm misunderstanding something.

Thanks again for helping...

P
  Reply With Quote
Old 22nd February 2005, 09:25 PM   #7
diyAudio Member
 
jeff mai's Avatar
 
Join Date: Aug 2002
Location: Melbourne
Default Re: Problem with my Darling!

Quote:
Originally posted by philipbarrett

3) input to 1626 (pin 5) = 34VAC
4) output from 1626 = 10.41VAC

yes Virginia it's an attenuator!
How are you measuring number 4? At the transformer secondary? At the 1626 plate?
  Reply With Quote
Old 22nd February 2005, 09:45 PM   #8
diyAudio Member
 
philipbarrett's Avatar
 
Join Date: Feb 2005
Location: Dallas, Texas
Send a message via AIM to philipbarrett
Thanks for your post. I am measuring at the 1626's plates (pin 3) using my 400Hz test tone. If I experiment with the transformer secondries I can get a little more gain (still not enough to be called an amplifier) to the speakers but at the expense of gross distortion.

P
  Reply With Quote
Old 22nd February 2005, 09:55 PM   #9
diyAudio Member
 
jeff mai's Avatar
 
Join Date: Aug 2002
Location: Melbourne
Quote:
Originally posted by philipbarrett
I am measuring at the 1626's plates (pin 3) using my 400Hz test tone.
The question had to be asked.

There's still something funny about your measurements. Otherwise your first stage has a gain of over 300! If the measurement at the output of the first stage / input of 1626 was instead 3.4VAC, everything would look pretty normal. 88mV of input isn't going to result in much power output and I believe the amp itself has very little overall voltage gain anyway. 1 Watt referenced to 8 ohms is only 2.8Vrms. My CD player has as much output! (Of course, it'd never source enough current to drive a pair of speakers.)
  Reply With Quote
Old 23rd February 2005, 06:40 AM   #10
diyAudio Member
 
philipbarrett's Avatar
 
Join Date: Feb 2005
Location: Dallas, Texas
Send a message via AIM to philipbarrett
I just re-confirmed, those voltages are correct.

P
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
A Darling.......ton Story .... east electronics Solid State 19 12th November 2011 11:12 AM
Darling 1626 amp rca9449 Tubes / Valves 9 7th October 2008 05:33 PM
which project for a darling amp kalinowski Full Range 4 28th May 2008 08:30 PM
Darling in Europe... (110 vs. 220) opopanax666 Tubes / Valves 12 31st March 2008 07:26 AM
Darling monoblocks Greyskale Tubes / Valves 3 13th March 2008 11:25 PM


New To Site? Need Help?

All times are GMT. The time now is 11:57 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2