Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Solid State => Topic started by: CraigB on April 19, 2009, 03:42:42 pm

Title: relay for footswitch in HoSo 56
Post by: CraigB on April 19, 2009, 03:42:42 pm

I have no experience with switching relays at all, but I'd like to make the boost as shown on da Geezer's HoSo 56 schematic footswitchable using a DPDT relay.  My power tranny has a 27-0-27v tap that is unused, can that be used as the power source to power the relay?  Can anybody point me to schematics/layouts of what I'm after?   Thanks

Title: Re: relay for footswitch in HoSo 56
Post by: Fresh_Start on April 19, 2009, 10:21:23 pm

Try the SEARCH function here and in the Library.  Doug's 18-Watt Stout uses a relay to switch a preamp stage in & out.  Maybe you can start with that.  Also, the "Solid State" section here may be a good source of info.

Sorry I don't know enough to answer your question.

Chip

Title: Re: relay for footswitch in HoSo 56
Post by: Geezer on April 21, 2009, 07:57:57 am

I cheated  :-[ ..... I used a Weber Relay board (low power).  $10 for the kit, or $14 assembled.

Here's the pic & description>>>
https://taweber.powweb.com/store/chansw.htm (https://taweber.powweb.com/store/chansw.htm)

Here's the catalog page>>>
https://taweber.powweb.com/store/chansword.htm (https://taweber.powweb.com/store/chansword.htm)

Doug sells the "raw" relays & has a good description of "how to" in "The Tube amp Library of information" link at the bottom of this page.

Here's a start>>>
http://www.el34world.com/projects/relay_switch.htm (http://www.el34world.com/projects/relay_switch.htm)

Title: Re: relay for footswitch in HoSo 56
Post by: PRR on April 22, 2009, 12:37:03 am

> My power tranny has a 27-0-27v tap that is unused, can that be used as the power source to power the relay? 

Hoffman's relays are 5V at unspecified current. That's a big mismatch from your 27V-38VDC, and not enough data to suggest a simple kludge.

24VDC DPDT relays are readily available. Here's an 8mA job, four bucks, hundreds in stock.

www.mouser.com search on "G5A-237P-DC24"
G5A-237P-DC24 datasheet (http://www.components.omron.com/components/web/pdflib.nsf/0/D0DDB2DCAD0550AC85257201007DD68D/$file/G5A_0607.pdf)

Use Hoffman's plans, except change 4700uFd to 470uFd 50V, insert 1K between that cap and relay/LED node, change LED resistor to 4.7K.

Title: Re: relay for footswitch in HoSo 56
Post by: CraigB on May 04, 2009, 12:16:28 pm

Thanks for the info guys - Craig