Image

2x2sc2879 amp questions

This is the place to ask questions about linear amplifiers, or power supplies

Moderator: JR Moderator

User avatar
Lerch256
Mud-Duck Jr.
Mud-Duck Jr.
Posts: 4
Joined: Thursday, 18 November 2010, 0:32 AM
Radio: Galaxy 99v
Name: Lerch

2x2sc2879 amp questions

Post by Lerch256 » Saturday, 28 January 2017, 18:12 PM

Hello I have attempted to build a 2 transistor amplifier seems to be working ok dead key 20 swing 100 bird 300 pep on bird but my question is I put the trimmers/tuners in and I tuned it best I know how I have 1/8 watt reflect on meter but it is at 200pf on input and 170pf on output does that seem correct?

Look at pics give me some advice or whatever your thoughts only issue is when I key it up and modulate I can kinda hear myself in the transistors


User avatar
543FtWorth
Wordwide & Qualified
Wordwide & Qualified
Posts: 1617
Joined: Sunday, 18 July 2010, 17:54 PM
Radio: (non-sponsor) 29 LTD
Antenna: *Censored*

Re: 2x2sc2879 amp questions

Post by 543FtWorth » Saturday, 28 January 2017, 21:23 PM

That's close if it's a dave made style amplifier. Usually 180pf on the input and 150pf on the output if memory serves me. The output transformers talking may be due to the output tuning being off or possibly a dirty radio.

User avatar
Crusher
Donor
Donor
Posts: 945
Joined: Saturday, 29 July 2006, 17:39 PM
Location: The Bluegrass

Re: 2x2sc2879 amp questions

Post by Crusher » Sunday, 29 January 2017, 4:30 AM

Don't see any pics. Also, what mix transformer and lengths since no pics

-- January 29 2017 --

Don't see any pics. Also, what mix transformer and lengths since no pics

User avatar
Lerch256
Mud-Duck Jr.
Mud-Duck Jr.
Posts: 4
Joined: Thursday, 18 November 2010, 0:32 AM
Radio: Galaxy 99v
Name: Lerch

Re: 2x2sc2879 amp questions

Post by Lerch256 » Tuesday, 31 January 2017, 23:04 PM

I have a 1/2x1/2 input transformer with 3 wraps of 16ga teflon and a 1 1/2x5/8 output transformer with 16ga teflon also wrapped twice

If I can figure out how to upload a pic I'll post one thanks

-- Tuesday, 31 January 2017, 23:15 PM --

Pic 1
You do not have the required permissions to view the files attached to this post.

User avatar
Crusher
Donor
Donor
Posts: 945
Joined: Saturday, 29 July 2006, 17:39 PM
Location: The Bluegrass

Re: 2x2sc2879 amp questions

Post by Crusher » Tuesday, 31 January 2017, 23:16 PM

So the output transformer is a comp style transformer. But the 1/2" x 1/2" input transformer, is that a 43, 61 or 67 mix?

-- January 31 2017 --

It looks like 61 mix which is good. It may take 200pf, but that is not a common value. 180&220pf are. If it needs 200pf, just parallel 2 x 100pf and call it good


User avatar
Lerch256
Mud-Duck Jr.
Mud-Duck Jr.
Posts: 4
Joined: Thursday, 18 November 2010, 0:32 AM
Radio: Galaxy 99v
Name: Lerch

Re: 2x2sc2879 amp questions

Post by Lerch256 » Tuesday, 31 January 2017, 23:24 PM

Pic 2
20170127_052851_opt.jpg
-- Tuesday, 31 January 2017, 23:37 PM --

Yes it is a type 61

I had a 3 wrap on the output but I changed it to a 2 wrap just messing around which would be correct or better in your opinion

Wish I would've went with the 1.25x5/8 output but I didn't know chalk it up to learning experience
You do not have the required permissions to view the files attached to this post.

User avatar
Crusher
Donor
Donor
Posts: 945
Joined: Saturday, 29 July 2006, 17:39 PM
Location: The Bluegrass

Re: 2x2sc2879 amp questions

Post by Crusher » Wednesday, 01 February 2017, 5:33 AM

Usually on that setup it is 3in, 2 out

User avatar
Lerch256
Mud-Duck Jr.
Mud-Duck Jr.
Posts: 4
Joined: Thursday, 18 November 2010, 0:32 AM
Radio: Galaxy 99v
Name: Lerch

Re: 2x2sc2879 amp questions

Post by Lerch256 » Wednesday, 01 February 2017, 17:18 PM

Thanks Crusher

When I got home last night I changed the output back to a 3 wrap it brought the bird watts up to 140 and the pep to 400 on the bird after playing with the tune still got 1/8 watt or so reflect but I have not checked the pf on the input or output yet will when I get home working night shift well my evenings ate from 2:30am to 7 or so lol

Does that sound right on the rms and pep on a 2 pill??
Or does that seem to be a little much?

-- Wednesday, 01 February 2017, 17:23 PM --

That's with a Galaxy 99 and into a 100 watt dummy load

-- Wednesday, 01 February 2017, 17:47 PM --

1000 watt dummy load

-- Friday, 03 February 2017, 16:43 PM --

Took it back to two wraps thank crusher


Post Reply Previous topicNext topic

Who is online

Users browsing this forum: No registered users and 2 guests