HRM needs some Lovin'

Overdrive Special, Steel String Singer, Dumbleland, Odyssey, Winterland, etc. -
Members Only

Moderators: pompeiisneaks, Colossal

Post Reply
fred.violleau
Posts: 503
Joined: Tue Jun 06, 2017 12:20 pm
Location: Montreal, Canada

Re: HRM needs some Lovin'

Post by fred.violleau »

Hi guys,

I must say working on this project is challenging, and I try to live this as a labor of love. I do my best to keep going and not be discouraged by all the things that need to be done before I can fire this amp back again.

I have almost finished the main board. I have trouble attaching the pfiher pots because the eyelets of the board don't match the spacing of the pots.
If you have any recommendation, I am up to it. The pfiher pots looks to be very little to operate. I might end up gluing bigger ones and on the board and wire it to the eyelets if I can't find a good replacement.


Image

After reading many threads on the forum, it seems like some cable should not run to close to others because of interferences and possible RF due to magnetic field generated by the trannies. It also looks like keeping the cables as short as possible is a best practice.

I have also started to overhaul the front panel to fit the HRM pots and then I realized that the amp layout is upside down : preamp tubes on the left side, trannies on the right side etc... It means that if I put the main board back with the tonestack located on the left, I will have to run all my cables opposite ways to connect them to the preamp tubes and pots.

Image

Questions :
1- can I reverse the position of the board so that all wires coming out of the board are facing all their connectors ?
2- there are lots of cables to connect, trying to keep things tidy as much as I can, I would like to use plastic wrappers to keep them together. Can I tie the tonestack wires together? which ones should not mingle? I am trying to figure things out from layouts pictures on the forum, but It is not that clear to me.

Thanks.

Fred.
You do not have the required permissions to view the files attached to this post.
ChopSauce
Posts: 1038
Joined: Wed Mar 15, 2017 12:08 pm
Location: So Paris, France

Re: HRM needs some Lovin'

Post by ChopSauce »

Do you mean that your new board is OK but the previous owner build everything else following a "mirrored" layout?

I have no precise idea about the subject, but I'll sure be tempted to buy a new chassis and build that properly, at that point.
fred.violleau
Posts: 503
Joined: Tue Jun 06, 2017 12:20 pm
Location: Montreal, Canada

Re: HRM needs some Lovin'

Post by fred.violleau »

Hi ChopSauce,

I have no clue why the builder of the amp has done thing in the opposite way.
I thought about re-doing the whole chassis. The problem is the wiring for all the tubes, power supply and power rectification.
I thought I would not touch the things that seems to work properly.

So in order to have the wires facing their connectors, I would have to flip the new board180 degrees.
I was wondering about what would happen if doing so (RF problems ? potential power oscillation? etc... ).
Otherwise, I have attached long enough wires on the board to have them run underneath . Not very Dumbly or kosher, but hey.. it is what it is ;)

I am almost done wiring it. It is missing the two pots one for the PI and one for the OD trimmer
Did not test it yet.

Cheers.

Fred.
User avatar
norburybrook
Posts: 3290
Joined: Mon Jan 06, 2014 12:47 am
Location: London
Contact:

Re: HRM needs some Lovin'

Post by norburybrook »

you can splay out the legs of the trimmer pots. Most of my builds with pre made boards have had eyelets that didn't match with the pots. Some gentle persuasion with some needle nose pliers will sort that out.

M
fred.violleau
Posts: 503
Joined: Tue Jun 06, 2017 12:20 pm
Location: Montreal, Canada

Re: HRM needs some Lovin'

Post by fred.violleau »

@nordburybrook, thanks for the tip!
I will work on my nose plier persuasion skill set ;)
User avatar
M Fowler
Posts: 14017
Joined: Wed Jan 16, 2008 2:19 am
Location: Walcott ND

Re: HRM needs some Lovin'

Post by M Fowler »

You need a new chassis and built it right. Where do you live?

Mark
fred.violleau
Posts: 503
Joined: Tue Jun 06, 2017 12:20 pm
Location: Montreal, Canada

Re: HRM needs some Lovin'

Post by fred.violleau »

Mark, I live in Montreal Canada.
fred.violleau
Posts: 503
Joined: Tue Jun 06, 2017 12:20 pm
Location: Montreal, Canada

Re: HRM needs some Lovin'

Post by fred.violleau »

I could not get my hands on a 2K pot for the presence knob. I have a 1K and a 5K pot. I thought about using a resistor on the 1K pot to match the 2K requirement but then I will always have at least 1K resistance engaged in the circuit. Is there a way to trick it differently? Should I use the 1K or 5K pot ?


Fred, learning everyday!


User avatar
martin manning
Posts: 13080
Joined: Sun Jul 06, 2008 12:43 am
Location: 39°06' N 84°30' W

Re: HRM needs some Lovin'

Post by martin manning »

You can put a 3k3 across the outer lugs of the 5k and get 1.99k, or put 1k in series with 1k pot. A linear pot will have most of the tonal variation in the upper half anyway, so 1k plus 1k in series would be better for spreading the effect over the whole rotation.
fred.violleau
Posts: 503
Joined: Tue Jun 06, 2017 12:20 pm
Location: Montreal, Canada

Re: RE: Re: HRM needs some Lovin'

Post by fred.violleau »

martin manning wrote:You can put a 3k3 across the outer lugs of the 5k and get 1.99k, or put 1k in series with 1k pot. A linear pot will have most of the tonal variation in the upper half anyway, so 1k plus 1k in series would be better for spreading the effect over the whole rotation.
Thanks Martin, much appreciated!

Fred, learning everyday!

User avatar
M Fowler
Posts: 14017
Joined: Wed Jan 16, 2008 2:19 am
Location: Walcott ND

Re: HRM needs some Lovin'

Post by M Fowler »

Fred, I'll check my 2k pot drawer their alpha.

Mark
User avatar
didit
Posts: 976
Joined: Thu Sep 25, 2008 3:37 pm
Location: Canada

Re: HRM needs some Lovin'

Post by didit »

M Fowler wrote: Mon Aug 21, 2017 11:12 pm You need a new chassis and built it right. Where do you live?
fred.violleau wrote: Tue Aug 22, 2017 10:22 am Mark, I live in Montreal Canada.
Seaside is still in operation. Terry could provide a clean fresh-start chassis.

See 1650HA OPT. Curious regarding the power transformer.

Best .. Ian
User avatar
dorrisant
Posts: 2613
Joined: Tue Sep 21, 2010 1:27 pm
Location: Somewhere between a river and a cornfield
Contact:

Re: HRM needs some Lovin'

Post by dorrisant »

Lookin' good so far! kudos for diving in to the deep end...
"Education is what you're left with after you have forgotten what you have learned" - Enzo
fred.violleau
Posts: 503
Joined: Tue Jun 06, 2017 12:20 pm
Location: Montreal, Canada

Re: HRM needs some Lovin'

Post by fred.violleau »

@Ian thanks for the reference I will definitely call them.

@Mark I think I can get along with Martin's option, but I really appreciate the gesture.

@Dorrissant thanks for the support!


Fred, learning everyday!

fred.violleau
Posts: 503
Joined: Tue Jun 06, 2017 12:20 pm
Location: Montreal, Canada

Re: RE: Re: HRM needs some Lovin'

Post by fred.violleau »

didit wrote:
M Fowler wrote: Mon Aug 21, 2017 11:12 pm You need a new chassis and built it right. Where do you live?
fred.violleau wrote: Tue Aug 22, 2017 10:22 am Mark, I live in Montreal Canada.
Seaside is still in operation. Terry could provide a clean fresh-start chassis.

See 1650HA OPT. Curious regarding the power transformer.

Best .. Ian
1650HA is the actual tranny used on this build.

Image

Fred, learning everyday!

Post Reply