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Philco TPA-1 - Printable Version

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RE: Philco TPA-1 - tim1 - 01-19-2014

I did disconnect the crystal for the first test on the test where you disconnect r2 do you have to disconnect the crystal?

RE: Philco TPA-1 - morzh - 01-19-2014

As I said before: disconnect from transformer.
No you don't have to disconnect crystal - the R2 disconnect does it automatically.

RE: Philco TPA-1 - tim1 - 01-19-2014

The person who comes over could not find r2 on the schematic have to find different helper is it on the smaller transformer or the larger one thanks

RE: Philco TPA-1 - morzh - 01-19-2014

According to the schematic you listed R2 is between the output of the first transformer and L5021 transistor's base. It is 470 Ohm.

RE: Philco TPA-1 - tim1 - 01-20-2014

I did what you suggested and hooked a earphone line on the leg of the resistor and at high volume it sounded clearer and when I turned the volume it sounded broken up sound not clear.

RE: Philco TPA-1 - morzh - 01-20-2014

Tim

1. I apologize, I meant between the R2 and the "Negative of C1" (where R3, R4, C1 negative and the transformer come together). Can you repeat it? If it still is broken on the low volume:

Can you do the following:

With the whole thing turned on (when you connect the musical source or when you play a record), can you measure the voltage between:

1. the Ground and the "-3V" battery terminal?
2. the Ground and the lower (according to the schematic) L5022 transistor's Collector terminal (the one going to -3V)? Measure right at the terminal.
3. the Ground and upper transistor's Emitter?
4. the ground and "+3V" battery terminal?

When measuring voltage on batteries' terminal, measure at actual spring contacts or better yet and NOT on the batteries own contacts. Better yet measure at the point where wires solder to those contacts.
What I want to know is what voltage the actual schematic is seeing. The contacts may be dirty or oxidized and I want to exclude it.


Additional:

With unit OFF:

1. try to measure with Ohmmeter across both transformers' primary and secondary windings.
When measuring wait for a few seconds making the result is stable (there is a capacitor there).
list the readings here.

For the first transformer they are 3700/120 Ohms for primary/secondary.
For the secondary they are 150 for primary and 14.5 for both secondaries.

2. Measure resistors R2 through R10. List the values.

RE: Philco TPA-1 - tim1 - 01-20-2014

I connected the headphone lead to the neg side of the c1 capacitor and the same sythoms occurred. I am going to get help solder the resistor back on the transformer and measure voltages.

RE: Philco TPA-1 - morzh - 01-20-2014

ok good.

RE: Philco TPA-1 - morzh - 01-23-2014

Tim

Any news?

RE: Philco TPA-1 - tim1 - 01-23-2014

I was trying to get help in showing me which one to use as ground and check each battery terminal like you said

RE: Philco TPA-1 - morzh - 01-23-2014

You could use the point between the two groups of batteries (you have 2+2 batteries, right?)

So the GND is the point where the first group of two batteries connect to the second group of two batteries.
This point is also present on the S1 switch which connects the two groups together.

or you could use the lower point of the R1 volume regulator - it also connects to GND.

RE: Philco TPA-1 - tim1 - 01-26-2014

I am waiting for a meter that has the button on the probe so I can measure easier. The Chinese meter I have has the button on the meter.

RE: Philco TPA-1 - tim1 - 02-03-2014

I hooked the plus lead of the volt meter to the plus terminal farthest from the front of the machine and I put the negative on one spring and I got 2.99 and on the other spring I got 6 volts. I switch to the other positive wire fclosest to the speaker and one spring got 2.99 volts and the other spring said 0 volts with the machine turned on.

RE: Philco TPA-1 - morzh - 02-03-2014

Tim

as you probably understand we do not know what "farthest spring from the front" and the other spring and the "closest to the speaker" mean in schematic turns.

Please try to speak in schematic terms, and give me measurements relative to GND, whatever spring or contact it might be.

Both device turned on and turned off.

You also want to measure BEFORE the spring contact and AFTER to eliminate oxidizing as a possible reason for bad behaviour.

PS> Meantime if what you told means one battery either loses voltage / gets shorted / the contact is oxidized is true (so far I am surmising) we might have a bad transistor. But again, I am absolutely not sure I understood what you wrote so far.

RE: Philco TPA-1 - tim1 - 02-03-2014

I got some one to tell me colors. when I test the blue with the black I get 3 volts and from red to orange I get 3 volts. When I test blue to orange I get 6 volts and when I go from red to black I get 0 volts.