UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Other Discussions > Homebrew Equipment

Notices

Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members.

Reply
 
Thread Tools
Old 17th Apr 2019, 1:08 pm   #21
Miguel Lopez
Heptode
 
Miguel Lopez's Avatar
 
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 552
Default Re: Building a little practical audio amplifier for experimentation

Quote:
Originally Posted by Andy
what are those trimmer pots for?
To adjust the center "tap" of the heaters, both on the amplifier and rectifier valves, to reduce hum

Quote:
Originally Posted by Andy
are you still using aspirin as flux?
I am. But those soldering that you see on the PCB were done using the solder that you once sent me. That's why it looks shinning. That solder is reserved for important projects only.

Quote:
Originally Posted by David
use insulating 'top hat' bushes on the screws.
I will use insulating sleeves and bakelite or fiberglass washers.
__________________
When electrons move, things happen.
There's nothing you can do that can't be done.
Miguel Lopez is offline   Reply With Quote
Old 13th May 2019, 5:56 pm   #22
Miguel Lopez
Heptode
 
Miguel Lopez's Avatar
 
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 552
Default Re: Building a little practical audio amplifier for experimentation

As Mr Time, the "Implacable", has no mercy of this humble mortal, I'm advancing very slow with this project, as usual. Anyway I have done some advances that I want to share with you. It is already working althought I have not tested it with audio nor a speaker, just a 1kHz signal from my signal generator. The sine wave was clean for a power of about 3W, which is more than enough for what I want. I powered a 10 ohms dummy load.
Attached Thumbnails
Click image for larger version

Name:	resized_DSCN1627.jpg
Views:	229
Size:	46.4 KB
ID:	183010   Click image for larger version

Name:	resized_DSCN1615.jpg
Views:	216
Size:	52.9 KB
ID:	183011   Click image for larger version

Name:	resized_DSCN1633.jpg
Views:	230
Size:	54.8 KB
ID:	183012   Click image for larger version

Name:	resized_DSCN1635.JPG
Views:	215
Size:	57.8 KB
ID:	183013   Click image for larger version

Name:	resized_DSCN1632.JPG
Views:	207
Size:	49.7 KB
ID:	183014  

__________________
When electrons move, things happen.
There's nothing you can do that can't be done.
Miguel Lopez is offline   Reply With Quote
Old 13th May 2019, 9:02 pm   #23
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 5,466
Default Re: Building a little practical audio amplifier for experimentation

That is a very impressive construction method....looks like a piece of restored military kit! Well done!
__________________
On Spike Milligan's headstone......I told you I was ill...
Sideband is offline   Reply With Quote
Old 18th May 2019, 7:56 pm   #24
Skywave
Dekatron
 
Skywave's Avatar
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 6,495
Question Re: Building a little practical audio amplifier for experimentation

I'm probably mistaken about this, but looking at R9, the phasing connections of the O/P transformer and the grid-anode phase relationships of the valves, isn't that feedback via R9 in-phase with any signal appearing on the grid of the first triode - thus increasing the chance of instability?

Al.
__________________
Never act on your first idea. Like solving a crossword clue, a better idea arrives tomorrow.
Skywave is offline   Reply With Quote
Old 18th May 2019, 11:17 pm   #25
Paul JD
Pentode
 
Join Date: Oct 2018
Location: Coventry, West Midlands, UK.
Posts: 173
Default Re: Building a little practical audio amplifier for experimentation

The feedback is going to the cathode of the input stage so it needs to be in phase with the signal on the grid in order to produce negative feedback.
Paul JD is offline   Reply With Quote
Old 5th Jul 2019, 3:26 pm   #26
Miguel Lopez
Heptode
 
Miguel Lopez's Avatar
 
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 552
Default Re: Building a little practical audio amplifier for experimentation

I'm advancing very slow on this project due to lack of available time. Anyway I have begun to build the input block with the three different plugs, which will be connected in "star".
Attached Thumbnails
Click image for larger version

Name:	DSCN1713.JPG
Views:	146
Size:	111.1 KB
ID:	186212   Click image for larger version

Name:	DSCN1714.JPG
Views:	134
Size:	110.1 KB
ID:	186213  
__________________
When electrons move, things happen.
There's nothing you can do that can't be done.
Miguel Lopez is offline   Reply With Quote
Old 30th Jul 2019, 9:31 pm   #27
Miguel Lopez
Heptode
 
Miguel Lopez's Avatar
 
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 552
Default Re: Building a little practical audio amplifier for experimentation

On last weekend I did some advances on this project. I mounted the shield between the transformers and the signal lines (input conectors and volume potentiometer), and also put the input connectors on their place. I played music with the amp for the whole weekend althought it is not finished yet. I have to build the front panel and the built-in speaker cabinet. See some pictures
Attached Thumbnails
Click image for larger version

Name:	resized_DSCN1720.JPG
Views:	95
Size:	41.9 KB
ID:	187593   Click image for larger version

Name:	resized_DSCN1721.jpg
Views:	80
Size:	35.0 KB
ID:	187594   Click image for larger version

Name:	resized_DSCN1722.jpg
Views:	67
Size:	26.5 KB
ID:	187595  
__________________
When electrons move, things happen.
There's nothing you can do that can't be done.
Miguel Lopez is offline   Reply With Quote
Old 23rd Sep 2019, 2:44 pm   #28
Miguel Lopez
Heptode
 
Miguel Lopez's Avatar
 
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 552
Default Re: Building a little practical audio amplifier for experimentation

This weekend I was able to resume working on this little project. Mr Time the "implacable" has been implacable with me but now I have been able to go on with this. I built the rest of the chassis, but I wasn't able to built the built-in speaker cabinet as the speaker that I have is too big, and there is no roon inside the chassis. I will go to my "war reserve" to find a flatter speaker to fit inside. Anyway I used it this way on weekend.
Attached Thumbnails
Click image for larger version

Name:	resized_DSCN1763.jpg
Views:	103
Size:	42.6 KB
ID:	190703   Click image for larger version

Name:	resized_DSCN1764.JPG
Views:	114
Size:	67.5 KB
ID:	190704  
__________________
When electrons move, things happen.
There's nothing you can do that can't be done.
Miguel Lopez is offline   Reply With Quote
Old 8th Oct 2019, 2:55 pm   #29
Miguel Lopez
Heptode
 
Miguel Lopez's Avatar
 
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 552
Default Re: Building a little practical audio amplifier for experimentation

Finally I found a suitable speaker and I fitted it inside the amplifier. It's from an old Soviet TV.
Attached Thumbnails
Click image for larger version

Name:	DSCN1779.jpg
Views:	88
Size:	42.6 KB
ID:	191524  
__________________
When electrons move, things happen.
There's nothing you can do that can't be done.
Miguel Lopez is offline   Reply With Quote
Old 11th Oct 2019, 4:45 pm   #30
Miguel Lopez
Heptode
 
Miguel Lopez's Avatar
 
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 552
Default Re: Building a little practical audio amplifier for experimentation

Yesterday I used this amplifier the whole day. It worked nicely, and it's now fully operational
Attached Thumbnails
Click image for larger version

Name:	resized_DSCN1782.JPG
Views:	101
Size:	36.6 KB
ID:	191709  
__________________
When electrons move, things happen.
There's nothing you can do that can't be done.
Miguel Lopez is offline   Reply With Quote
Old 11th Oct 2019, 5:39 pm   #31
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 4,708
Default Re: Building a little practical audio amplifier for experimentation

Good work mate, hope you have some brighter paint to paint than your usual battle ship grey or 70's nylon shirt brown : ) A nice bright orange would look well.

Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is online now   Reply With Quote
Old 11th Oct 2019, 8:47 pm   #32
Miguel Lopez
Heptode
 
Miguel Lopez's Avatar
 
Join Date: Dec 2011
Location: Mayabeque, Cuba
Posts: 552
Default Re: Building a little practical audio amplifier for experimentation

A phosphorescent pink or violet would be nice too, don't you think?
__________________
When electrons move, things happen.
There's nothing you can do that can't be done.
Miguel Lopez is offline   Reply With Quote
Old 12th Oct 2019, 2:22 am   #33
joebog1
Heptode
 
joebog1's Avatar
 
Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 952
Default Re: Building a little practical audio amplifier for experimentation

I must say Miguel, you do make a beautiful job. I must agree with Andy however
Soviet grey can be a bit over whelming. Superb job however.
Did the 807 and valve base come in handy ?

Best regards
Joe
joebog1 is offline   Reply With Quote
Old 12th Oct 2019, 4:27 pm   #34
usradcoll1
Hexode
 
Join Date: Mar 2017
Location: Cedar Grove, Wisconsin, USA.
Posts: 429
Default Re: Building a little practical audio amplifier for experimentation

Quote:
Originally Posted by Diabolical Artificer View Post
Good work mate, hope you have some brighter paint to paint than your usual battle ship grey or 70's nylon shirt brown : ) A nice bright orange would look well.

Andy.
Things are probably a bit different in Cuba!
Ours and your home improvement stores have just about any color paint in any finish you desire. Possibly, not the same there.
Fine job done there. Too bad you couldn't fit a larger speaker To do justice to the EL84 output valve and the larger output transformer.
Dave, USradcoll1, always interested!
usradcoll1 is offline   Reply With Quote
Old 14th Oct 2019, 12:18 am   #35
retailer
Pentode
 
Join Date: May 2005
Location: Adelaide, South Australia
Posts: 125
Default Re: Building a little practical audio amplifier for experimentation

Good job I'm sure you are pleased - while grey may not be the brightest colour around, paint, no matter the colour always improves the look of a project.
retailer is offline   Reply With Quote
Old 14th Oct 2019, 2:05 am   #36
fetteler
Heptode
 
fetteler's Avatar
 
Join Date: Jul 2011
Location: Staffordshire Moorlands, UK.
Posts: 713
Default Re: Building a little practical audio amplifier for experimentation

Miguel,

Please do not pay any attention to those who would make trivial comments about "Soviet" paint colours. One does not judge a book by its cover.
Your amplifier build is superb and I am sure you will have many happy hours listening to it.

Best wishes,
Steve.
__________________
Those who lack imagination cannot imagine what is lacking...

Last edited by fetteler; 14th Oct 2019 at 2:13 am.
fetteler is offline   Reply With Quote
Old 14th Oct 2019, 9:20 am   #37
alanworland
Heptode
 
alanworland's Avatar
 
Join Date: Feb 2011
Location: Southend, Essex, UK.
Posts: 594
Default Re: Building a little practical audio amplifier for experimentation

Miguel, trust you and yours are well.
Your amplifier looks superb and I am sure it will stand you well for all of its up and coming projects! Most test amplifiers I am sure remain at no more than a breadboard stage of assembly and get used that way for years.
Yours is a proper build.
(I'd be tempted to leave it unpainted!!)

Alan
alanworland is offline   Reply With Quote
Old 14th Oct 2019, 9:50 am   #38
PJC58-Hythe
Hexode
 
PJC58-Hythe's Avatar
 
Join Date: Sep 2010
Location: Hythe, Hampshire, UK.
Posts: 311
Default Re: Building a little practical audio amplifier for experimentation

Miguel,

Really nice to see proper 'homebrew' equipment, you have done an excellent job and should be proud of it!

All the best, and keep up the constructing!
__________________
Peter - M0HYT - BVWS Member

http://www.retroworkshop.co.uk
http://www.valveradios.co.uk
PJC58-Hythe is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 9:45 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.