Could you please share the schematic you've used here. I can not find it anywhere. There is a service manual but it's split in 2 pages and the schematic inside is not as good as the one you have here. Please share. Thanks.
I'm not sure now where I downloaded the diagrams from. However, you might find the links on the following page useful: www.retroisle.com/sinclair/zxspectrum/technical.php
I'm so glad I found this series of videos. Your videos are not only great for Spectrum repairs, but also perfect for learning about general electronics repair. Very nicely done sir. Thanks a lot.
I was looking at mine and C46 seems to be in the wrong way round. Yours is the same so I`ll put it back as it came out. It`s got a + on the wrong side on the board. OK I got to the end of the video lol. Thanks for clearing that up.
Capacitors that have leakage current often measure significantly higher capacitance than their marked value. This is because capacitance testers often use the time it takes for the cap to charge to a particular voltage to determine the capacitance. When the cap is leaking current, it takes longer to charge because some of the current is being lost, thus the meter erroneously reports a higher capacitance.
Hi there joules great video. I picked Hitachi system deck amp cassette and tuner for£15. Absolute bargain. I need to change the belts on D 35s. They'd melted. Any videos or suggestions would be gratefully received. Do you have an email? Regards
Hi there a bit above my pay grade but I have ha2700 with slight scratch noise when turning the balance. Can I squirt some contact cleaner (Halfords brand) on the pot inside? Got a full system for £15. Cassette needs new belts. Next job if I can find on youtube haha. Thank you. Interesting videos. Thank you
Hi there I've got a ha2700 it makes static sounds when I turn balance treble and bass. Could I squirt contact cleaner on them from the inside? Thank you
It is 2022. I have owned the PM3217 50MHz version for 25 years. It developed a fault so I re-capped it. I added a IEC socket to replace the cord. It still works and I still use it. It is still a good scope.
Hell ! can you help ? i own a zx spectrum sinclair 48k that doesn´t load the games. They just get errors when first game screen opens or crash during the doalings and green little squares on some loading drawings. I inserted that to check the upper RAM chips : PRINT PEEK 23732 + 256 * PEEK 23733 the value result was wrong it was 32863 instead of 6553 »»»» I tested all the 8 upper RAM chips group on the board below (right side not the logical ones) using a fully working sinclair 48k and all 8 are good.
Hi my AG H350. Teac amp is overheating as fan is not speeding up as temperature goes up. Any ideas would help not opened it yet I am an electronics engineer. Cheers sir
Great video. I’m at a loss as to what you did to get the trace showing on the screen. What did you change to get the power light to come on and the trace to appear? 🤔
Thanks, I look forward to going through these tests before powering up. I'm guessing it's normal for the large foil trace around the video output on the rear of the board to be all crinkled? I initially panicked upon seeing this but after watching a few videos I've seen the same thing on every machine.
I have black centre and white border and think problem is on upper RAM how to check it by multimetr? Should I replace all chips with TMS4164-15NL or just wich was broken?
Hmm, this circuit (the one using the 555) doesn't seem to work for me. My ZX81 doesn't have a back porch, and the line synchronization pulse is about 2.3 V, the rest is about 4V. To trigger the 555, we'd need to go below 1/3*5V (~1.667V). If anyone has a nice solution, I'm all ears. Otherwise I'll reply to myself when I have figured out something that works.
