Replaced the voltage regulator, now I'm not getting a TV signal

[irishgreencitrus]

Hey there.
I'm very new to the world of Spectrums and I bought my first one (an issue 2 ZX Spectrum) a while ago.
I know it works; I managed to soldier a wire to bypass the modulator and it gave me a composite signal (albeit green-tinged) so I decided to start replacing the aging components

I realised that it was common to also replace the voltage regulator, so today I desoldered and soldered a new one to the board. After powering it on just after soldering the voltage regulator (am yet to do any other modifications) there was no longer a composite signal being outputted, but either the speaker or the voltage coil started to whine. Checking the voltage with a multimeter, the voltage regulator seemed to be converting the 9V input at the barrel jack to a 5V signal correctly, so I'm not really sure what could've gone wrong.

Can someone point me in the right direction in troubleshooting this?

[1024MAK]

The coil on issue two boards normally is fairly noisy.

What voltages do you have on the -5V and the +9V?

Also, it’s not usual to replace the 7805 voltage regulator, unless a DC/DC converter is being fitted.

If you used a 7805, has the heatsink been properly fitted? Please describe what you did in detail.

And did you do any other work?

Mark

[irishgreencitrus]

No other work has been done apart from the composite mod which I already know works (although I used the non-soldering method as I didn't have a soldering iron at the time, however I am considering replacing it with the capacitor soldiered version).

The heatsink is yet to be fitted, however the Spectrum was not on long enough for the heat to be the cause, and after turning off the Spectrum, the regulator is cool.

The voltage regulator has 9.5V in, 5V out which is within the expected range I'm pretty sure.

[1024MAK]

And what about the voltages on the -5V (negative 5V) and the +12V supplies. You can test on IC13 (front left hand corner of the PCB).
Pin 1 is the -5V
Pin 8 is the +12V

Make sure you don’t slip when testing and short two adjacent pins.

When you press a keyboard key that normally produces key clicks, do you get key clicks from the speaker?

It would also be a good idea to double check your composite video modification.

Mark

[Golfareninsweden]

Hi!

I not a repair guy but i like to look att this youtube channel https://www.youtube.com/@HappyLittleDiodes regarding repairing spectrums.


Cheers.

C

[irishgreencitrus]

And what about the voltages on the -5V (negative 5V) and the +12V supplies. You can test on IC13 (front left hand corner of the PCB).
Pin 1 is the -5V
Pin 8 is the +12V

Make sure you don’t slip when testing and short two adjacent pins.

When you press a keyboard key that normally produces key clicks, do you get key clicks from the speaker?

It would also be a good idea to double check your composite video modification.

Mark

Hmmm…

I don't seem to be getting any key clicks from the speaker and clicking BEEP with the correct parameters as I found online doesn’t seem to be doing anything either.

Unfortunately my multimeter has had one of the probes break, so i’ll need to get a new one before doing any further testing.

Thanks Mark, let me know if there’s any other steps I can do for testing when I get a new multimeter