Leak Delta 30 Amplifier - One Channel Down - Page 5 - UK Vintage Radio Repair and Restoration Discussion Forum

Wage Slave · 4th Oct 2010, 10:11 am

Quote:

Originally Posted by Station X

R15 supplies collector current to T1 and bias to the base of T2. It being open circuit won't help matters at all. Replace it.

I will as soon as I can lay my hands on one!

Wage Slave · 4th Oct 2010, 10:36 am

Help! Will 1/2 a watt be sufficient for R15?

jjl · 4th Oct 2010, 10:49 am

Yes, a 470K 1/2W resistor will be fine to replace R15.

John

Wage Slave · 4th Oct 2010, 10:51 am

Quote:

Originally Posted by jjl

Yes, a 470K 1/2W resistor will be fine to replace R15.

John

Ta. It's on order. It will take a week or so to arrive. Annoying!

Station X · 4th Oct 2010, 11:17 am

Nothing like Maplin, Tandy, Radio Shack or Dick Smith Electronics in Japan then? That surprises me.

Wage Slave · 4th Oct 2010, 11:46 am

Quote:

Originally Posted by Station X

Nothing like Maplin, Tandy, Radio Shack or Dick Smith Electronics in Japan then? That surprises me.

I'm investigating but the language barriers make it really hard. There is of course Akihabara in Tokyo where you can buy absolutely anything out of the stalls in the arches under the railway lines.Then of course you can go off to enjoy a coffee in a maid cafe. Amazing place.

I don't live in Tokyo though. Far from it. I am asking if anyone I know in Yokyo is in the Akihabara area this week but all in all, if I buy it from the UK, I know I am getting the right thing and best of all I can do it all by myself.

Wage Slave · 4th Oct 2010, 11:50 am

Right. I checked ever other resistor on the board and they are all good with the possible exception of R27 (3.3k) reading 3.8K and R25 (3.3K) reading 4.02K. These are both bigger wire wound type resistors. Is that anything to worry about do you think?

Alistair D · 4th Oct 2010, 11:54 am

When you measured R32 in circuit was one of your probes connected the chassis of the amp?
The reason I am asking is that the there is a whole chunk of the circuit that is grounded via pin 19. A high restance could help explain the correct emitter voltage and high collector voltages on T4 and explain the funny resistance measurements,
If your probes were always connected to the board I am talking rubbish.

Al

Station X · 4th Oct 2010, 12:00 pm

If I'd known you had to get components from the UK I'd have happily have sent you a few resistors FOC. It's not as if I'm short of them.

It would be unusual for wirewound resistors to go high in value. They generally go open circuit due to a break in the wire, or low resistance due to adjacent turns touching. So long as they don't look discoloured I'd assume they're OK.

I'd put the circuit back together around T4 and T5 and check the voltages there again.

Wage Slave · 4th Oct 2010, 12:01 pm

Quote:

Originally Posted by Alistair D

When you measured R32 in circuit was one of your probes connected the chassis of the amp?
The reason I am asking is that the there is a whole chunk of the circuit that is grounded via pin 19. A high restance could help explain the correct emitter voltage and high collector voltages on T4 and explain the funny resistance measurements,
If your probes were always connected to the board I am talking rubbish.

Al

No no, I am well worth checking on.

Both probes were on the board when I was measuring that. The only time I had one clipped to the chassis was when measuring transistor voltages.

Wage Slave · 4th Oct 2010, 12:06 pm

Quote:

Originally Posted by Station X

If I'd known you had to get components from the UK I'd have happily have sent you a few resistors FOC. It's not as if I'm short of them.

It would be unusual for wirewound resistors to go high in value. They generally go open circuit due to a break in the wire, or low resistance due to adjacent turns touching. So long as they don't look discoloured I'd assume they're OK.

I'd put the circuit back together around T4 and T5 and check the voltages there again.

That's really kind of you. I have ordered them from Cricklewood along with the transistors. At least I hope I have ordered them. Their order system for overseas customers consists of emailing sales with your cc number. I haven't heard back from them yet.

If they get it out today I might even get them by the end of the week. It usually takes 4 to 6 days for things to get here.

Alistair D · 4th Oct 2010, 12:06 pm

As a double check have a look at the diagram there are a number of edge connector fingers all attached to the thick black line (ground) it is also connected to the chassis. With one probe touching the chassis you shoud see an ohm or 2 on each if these ground pins. Meter polarity should not matter here.
These connections may also be intermittent.

Al

Wage Slave · 4th Oct 2010, 12:10 pm

Quote:

Originally Posted by Station X

I'd put the circuit back together around T4 and T5 and check the voltages there again.

Yep. So that would just mean putting T5 back? C11 and C17 are out as well as T1 but they can stay out for now?

Wage Slave · 4th Oct 2010, 12:17 pm

Quote:

Originally Posted by Alistair D

As a double check have a look at the diagram there are a number of edge connector fingers all attached to the thick black line (ground) it is also connected to the chassis. With one probe touching the chassis you shoud see an ohm or 2 on each if these ground pins. Meter polarity should not matter here.
These connections may also be intermittent.

Al

Yep. I'm not quite sure what I should be testing here. The connection at the "fingers?" So for example, check that T1 emitter is connected to earth through "finger" 4.

Alistair D · 4th Oct 2010, 12:25 pm

Quote:

Originally Posted by Wage Slave

Quote:

Originally Posted by Alistair D

As a double check have a look at the diagram there are a number of edge connector fingers all attached to the thick black line (ground) it is also connected to the chassis. With one probe touching the chassis you shoud see an ohm or 2 on each if these ground pins. Meter polarity should not matter here.
These connections may also be intermittent.

Al

Yep. I'm not quite sure what I should be testing here. The connection at the "fingers?" So for example, check that T1 emitter is connected to earth through "finger" 4.

Sorry, yes it is ambiguous.
One probe on the chassis and the other probe to fingers 2, 8 and 19 (4 is not a ground) on the the board you have been working on. You are checking that there is a connection through the finger to the chassis of the amp.

Wage Slave · 4th Oct 2010, 12:27 pm

Quote:

Originally Posted by Alistair D

Quote:

Originally Posted by Wage Slave

Quote:

Originally Posted by Alistair D

As a double check have a look at the diagram there are a number of edge connector fingers all attached to the thick black line (ground) it is also connected to the chassis. With one probe touching the chassis you shoud see an ohm or 2 on each if these ground pins. Meter polarity should not matter here.
These connections may also be intermittent.

Al

Yep. I'm not quite sure what I should be testing here. The connection at the "fingers?" So for example, check that T1 emitter is connected to earth through "finger" 4.

Sorry, yes it is ambiguous.
One probe on the chassis and the other probe to fingers 2, 8 and 19 (4 is not a ground) on the the board you have been working on. You are checking that there is a connection through the finger to the chassis of the amp.

Will do. I need to look more carefully!

Alistair D · 4th Oct 2010, 12:36 pm

I am still not clear enough in my descrription. (it al seems very clear to me but then I have been doing this kind of work 30 odd years).

On the diagram you will see that one side of R32 is connected to finger 19. Connect one probe of your meter to this point on the resistor when the board is in place. The other probe to the chassis. the resistance should be 1 ohm or less.

Please dont be afraid to keep asking until you are clear about what I am asking.

Al

Wage Slave · 4th Oct 2010, 12:45 pm

Quote:

Originally Posted by Alistair D

I am still not clear enough in my descrription. (it al seems very clear to me but then I have been doing this kind of work 30 odd years).

On the diagram you will see that one side of R32 is connected to finger 19. Connect one probe of your meter to this point on the resistor when the board is in place. The other probe to the chassis. the resistance should be 1 ohm or less.

Please dont be afraid to keep asking until you are clear about what I am asking.

Al

No no that's fine. Understood. I was just berating myself for not noticing pin 4 isn't connected to ground. Just crossing it. At one stage didn't diagrams have a loop in the line to show this?

Wage Slave · 4th Oct 2010, 1:10 pm

Quote:

Originally Posted by Alistair D

Quote:

Originally Posted by Wage Slave

Quote:

Originally Posted by Alistair D

As a double check have a look at the diagram there are a number of edge connector fingers all attached to the thick black line (ground) it is also connected to the chassis. With one probe touching the chassis you shoud see an ohm or 2 on each if these ground pins. Meter polarity should not matter here.
These connections may also be intermittent.

Al

Yep. I'm not quite sure what I should be testing here. The connection at the "fingers?" So for example, check that T1 emitter is connected to earth through "finger" 4.

Sorry, yes it is ambiguous.
One probe on the chassis and the other probe to fingers 2, 8 and 19 (4 is not a ground) on the the board you have been working on. You are checking that there is a connection through the finger to the chassis of the amp.

2 and 19 connect nicely. 8 doesn't but is 8 in fact an earth?

Alistair D · 4th Oct 2010, 1:17 pm

You are correct I am misreading the letter B for 8.
At least we have ruled out another possibility.
As Station X says go ahead and try it out.

Al

4th Oct 2010, 10:36 am	#82
Wage Slave Hexode Join Date: Sep 2010 Location: Tsu, Japan. Posts: 452	Re: Leak Delta 30 Amplifier - One Channel Down Help! Will 1/2 a watt be sufficient for R15?

4th Oct 2010, 10:49 am	#83
jjl Octode Join Date: Jan 2003 Location: Ware, Herts. UK. Posts: 1,082	Re: Leak Delta 30 Amplifier - One Channel Down Yes, a 470K 1/2W resistor will be fine to replace R15. John

4th Oct 2010, 11:17 am	#85
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Leak Delta 30 Amplifier - One Channel Down Nothing like Maplin, Tandy, Radio Shack or Dick Smith Electronics in Japan then? That surprises me. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

4th Oct 2010, 11:50 am	#87
Wage Slave Hexode Join Date: Sep 2010 Location: Tsu, Japan. Posts: 452	Re: Leak Delta 30 Amplifier - One Channel Down Right. I checked ever other resistor on the board and they are all good with the possible exception of R27 (3.3k) reading 3.8K and R25 (3.3K) reading 4.02K. These are both bigger wire wound type resistors. Is that anything to worry about do you think?

4th Oct 2010, 11:54 am	#88
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Leak Delta 30 Amplifier - One Channel Down When you measured R32 in circuit was one of your probes connected the chassis of the amp? The reason I am asking is that the there is a whole chunk of the circuit that is grounded via pin 19. A high restance could help explain the correct emitter voltage and high collector voltages on T4 and explain the funny resistance measurements, If your probes were always connected to the board I am talking rubbish. Al __________________ I won't tell you how I discovered that.

4th Oct 2010, 12:00 pm	#89
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	Re: Leak Delta 30 Amplifier - One Channel Down If I'd known you had to get components from the UK I'd have happily have sent you a few resistors FOC. It's not as if I'm short of them. It would be unusual for wirewound resistors to go high in value. They generally go open circuit due to a break in the wire, or low resistance due to adjacent turns touching. So long as they don't look discoloured I'd assume they're OK. I'd put the circuit back together around T4 and T5 and check the voltages there again. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

4th Oct 2010, 12:06 pm	#92
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Leak Delta 30 Amplifier - One Channel Down As a double check have a look at the diagram there are a number of edge connector fingers all attached to the thick black line (ground) it is also connected to the chassis. With one probe touching the chassis you shoud see an ohm or 2 on each if these ground pins. Meter polarity should not matter here. These connections may also be intermittent. Al __________________ I won't tell you how I discovered that. Last edited by Alistair D; 4th Oct 2010 at 12:08 pm. Reason: Added last sentence

4th Oct 2010, 12:36 pm	#97
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Leak Delta 30 Amplifier - One Channel Down I am still not clear enough in my descrription. (it al seems very clear to me but then I have been doing this kind of work 30 odd years). On the diagram you will see that one side of R32 is connected to finger 19. Connect one probe of your meter to this point on the resistor when the board is in place. The other probe to the chassis. the resistance should be 1 ohm or less. Please dont be afraid to keep asking until you are clear about what I am asking. Al __________________ I won't tell you how I discovered that.

4th Oct 2010, 1:17 pm	#100
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Leak Delta 30 Amplifier - One Channel Down You are correct I am misreading the letter B for 8. At least we have ruled out another possibility. As Station X says go ahead and try it out. Al __________________ I won't tell you how I discovered that.