loss of volume when linked input

[jujub]

Hi to all

It's been a month since got my new 1970 DR103, serial number is 1083. It is original exept for a recap an bias doubler mod.
I come to you because think something is wrong. when I link brilland on the low input and normal channel ther's a significant volume loss. that doesn't happen on my SA212 combo (74')


also alone I find that the brillant channel is less power full thant the normal one.

I've tried to change the preamp and output tube but it didn't changed anything.

Do you have any Idea?

Thanks

[Dr.HI-TONE]

post some pics of the input jack assembly and the preamp board associated with V1 and V2.

[jujub]

Here you are sir,

As you can see the 'middle' pot has been changed also 1 tone stack capacitor for bass was return to original mullard at 47n

INPUT JACKS

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TAG BOARD

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As you can see this amp is late 1970 (at least october) and so the layout is not the usual one !

Thank you !

[jujub]

I just saw that the middle pot value is wrong...50K instade of 100k...

[Dr.HI-TONE]

That tone stack is not the classic 1971-1974 tone stack. but I don't see a clear problem.
maybe Mark will see something?

[jujub]

That's why I was asking...didn't see anything wrong too

[Dr.HI-TONE]

has the bias capacitor been replaced since the pic was taken?

[mhuss]

Does it do this both ways, i.e., jumpering Normal to Brill versus jumpering Brill to Normal?

[jujub]

Yes. no matter how I connect when an input is connected to 'low' ...the output is 'low'.

I should mention that I found brillant Input is 'kind' of weaker than the normal one.

[mhuss]

Did you try replacing V1 (or swapping it with another)?

[jujub]

Yes I did. I changed every tubes in there without success

[mhuss]

I'm not sure how you're jumpering, but if you go into the low gain input and jumper that high into the other low gain input, you're going to have a pretty weak signal. The optimal way is to go into the high gain input and jumper that Low to the other channel high.

[jujub]

Here's what I do... as for the others Hiwatt I got

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[mhuss]

That looks fine. The only other thing I can think of is to test the values of the 220k resistors and 22n & 1n caps shown in your first pic above, and if they're OK, check the 2k2 cathode resistors and cap.

[jujub]

That big boy gone up to 250nF

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