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1

General Discussion Area / Re: Proof that Trump is insane

« on: 07 January 2026, 14:41:57 »

Trump doesn't need to invade.

I believe there is a small US military base there.

There are several VERY large US bases there.

The question is what would assorted European countries do if he did this?

The most convincing thing european countries could do is for Spain, France and Hungary to deny US military overflight and landing permissions. If they did that there would be no way for the US to support their 'friends' is Israel, Saudi or further east by air. The highest priority stuff could still get there using air to air tankers via the Gibraltar gap, but it gets difficult, and expensive very quickly if the tankers can't take off, land or overfly France or Spain. France already has a reputation for being a bit 'fussy' with diplomatic clearances for mil aircraft.

2

General Discussion Area / Re: car stereo question

« on: 04 January 2026, 16:58:03 »

The best circuit that I've found that most resembles your description is for the blaupunkt_rcr87_essen_rcr127. You can download that from here : https://elektrotanya.com/blaupunkt_rcr87_essen_rcr127.pdf/download.html

It may not be identical in every respect to your radio - but the tape and audio sections at least sound to be the same.

Once you've got the circuit it's usually fairly easy to diagnose audio faults, although it's much easier if you can follow the audio path through using an oscilloscope. More modern radios tend to be digital all the way through, so they are much more of  challenge, especially if virtually all the circuity has been integrated into a single chip.

3

General Discussion Area / Re: car stereo question

« on: 29 December 2025, 14:27:57 »

If I'm looking at the correct circuits - the resistor is R1310, a 1Kohm, connected between the base of V1310 (a PNP BC808) and pin 6 of connector P1530/N1530. When pin 6 of the connector is shorted to ground (by a microswitch on the tape deck) the transistor will conduct causing the mute circuits to activiate. The microswitch should be open circuit in normal tape operation. There is no resistor shown to pull the base high or keep the transistor "off", so the base is indeed floating during normal operation.

Lifting R1310, or disconnecting the wire into pin 6 of P1350, will have the same effect - and will stop the mute circuit from working. However, if that works it's not a leaky transistor - it's a problem with the wiring to the connector or the microswitch. However, it might be worth wiring a high value resistor (10K or more) between pins 3 and 6 on the connector. Pin 3 should be a stable 5V supply, and 10K should be more than enough to ensure the transistor (V1310) stays off when it should be off.

PS - I'm dying with man-flu at the moment, so might not be able to add any more unless I make a miraculous recovery.

4

General Discussion Area / Re: car stereo question

« on: 27 December 2025, 22:36:54 »

None of the circuits seem to show a 'second stage of preamp' as such. The rcr87_essen circuits show the tape preamp (an RC4558) feeding a couple of transistors (V1120 and V1130 both BC549C's), and from there into the TDA7348.

This is also where the tape mute circuit comes in - transistors V1310 (BC808), V1311(DTC1432KA), V1312(BC848C) and V1313(BC848C). This is where it gets sort of interesting. The Mute circuit appears to be fed from a couple of microswitches mounted on the cassette mechanism, via connector P1350/N1950. It looks like pin 2 of this connector should go to +5V when the cassette is inserted. Pin 6 of the connector should be open circuit when not-muted, and shorted to ground by a second microswitch when muted.

It's not obvious from the circuits what controls the microswitches, but I'd guess it's loading and unloading the cassette tape. I'd be much more suspicious of these microswitches than any semiconductor device. Given the 'single fault affecting both L&R channels' issue, it's most likely the feed to the base of V1310 is dicky - from pin 6 of P1350/N1950.

5

General Discussion Area / Re: car stereo question

« on: 22 December 2025, 23:33:18 »

I think it's going to be a struggle to diagnose without an oscilloscope.

The TDA7348 appears to have 3 identical stereo inputs. Pins 8 & 12 for the radio, 9 & 13 for the tape, and 10 & 14 for 'Aux' which I'm guessing is the CD in this instance.

The tape head pre-amp looks like it's a dual op amp - either an RC4558 or LM833. However, there is a mute circuit between the output of the preamp and the tape input of the TDA7348 which is controlled by the microprocessor. If the mute is being turned on and off rapidly it could sound like distortion and would affect both L & R channels.

So basically I'd want to 'scope the output of the preamp, the input to the TDA7348, and the mute circuitry. It should be obvious from these where the distortion is occurring.

6

General Discussion Area / Re: car stereo question

« on: 22 December 2025, 20:33:30 »

Ok, survived Clarks village - just.

Thinking about it on the drive home, it seems unlikely that you would get distortion on both left and right channels due to a single fault if the fault is in a capacitor or resistor. I mean all the circuits I've looked at the signal path is basically separate for L and R, so a single capacitor in the signal path going duff might distort one channel or t'other but not both. The chances of both L&R capacitors failing at the same time is tiny, and the chances of the same thing happening on multiple radios? Nahh, Occam's razor says it's something else.

You mention a TDA4748. Are you sure of that part number - or could it be a TDA7348? TDA7348 appears to be an audio processor & switch, switching the input between radio and tape inputs, and is used in lots of Blaupunkt stuff. TDA4748 is an obsolete switch mode power supply chip, and I can't see it on any of the circuit diagrams I've found.

The other possibility is power supply. When the tape deck motor is running the unit will probably be drawing 1A-2A more that when it's running on radio or CD. I'm wondering if this extra power is enough to cause the supply to drop and/or get noisy, enough to upset the supplies to the analogue sections of the tape and speaker drive circuitry. That would be enough to cause distortion on the 'tape' inputs, but allow the radio and CD to operate normally. It would also affect both L & R of the tape equally. It might also explain why if you pick off the tape signals and feed them into an external amp there is no distortion - the speaker drivers will also take a lot of power - perhaps there is only enough power to rune either the amps or the motors, and not both?

To test that theory I'd locate the supply pin to the tape deck - probably +12V - and power it externally from a bench supply. Need to be careful though - you don't want to blow up the cassette motors.

7

General Discussion Area / Re: car stereo question

« on: 22 December 2025, 16:59:38 »

Can't see it being related to motor speed. That would normally result in either slow/fast playback or more likely a wow-ing type variation in the audio output as the motor speed hunts up and down.

My first guess would have been it's related to tape pickup head alignment. It doesn't take much misalignment on the tape/head to cause a muffled type sound. However, if I understand correctly you're saying you've picked off the signal prior to the main amplifier and played it through a different amp, and it sounds ok? If that's correct, then probably not alignment.

Have you got a signal generator and an oscilloscope? If so you can usually inject a signal somewhere close to the tape pickup heads and then follow it through the circuit using the scope to see where the distortion is introduced. I'd go with a 1KHz signal at low amplitude (perhaps a few mV) to start with and crank up the amplitude once you're happy. Distortion on pure sine waves is usually pretty easy to spot by eye (on a 'scope), and even easier to hear.

There are some fairly complex frequency compensation circuits on cassettes due to the different charicteristics of various metals used in the tapes, plus other compression stuff (Dolby B/C for example). Don't rule out faults in these compensaiton circuits.

Haven't got time to look deeper today - need to go to Street/Clarks Outlet centre tonight. Shops close at 7pm and parking is only free after 6pm so a narrow window to get in and out without paying.  Not looking forward to it. 

8

General Discussion Area / Re: car stereo question

« on: 10 December 2025, 21:30:36 »

The circuits seem to cover lots of models - all basically the same, but followed by another city or state name. Cleveland, Dresden, Boston, Madison, Freiburg, Las Vegas, Canberra, San Diego, Essen, Alicante, Lausanne, Konstanz, San Remo, Santa Cruz, Dusseldorf, Kansas, Bologna, Hawaii, Maryland, Munchen or Modena.

Is there a numeric part number on the radio? I think the San Diego DJ RCR 127 should be "8 646 713 310"

9

General Discussion Area / Re: car stereo question

« on: 09 December 2025, 23:30:54 »

Is it one of these? https://elektrotanya.com/blaupunkt_san_diego_dj31_sch.pdf/download.html

If it is you can download the circuit diagrams from the link on that page.

It looks like the processor on the faceplate (Page 24) is only used to interface the various front panel keys. Communication with the main board is over an SPI (Serial Peripheral Interface) using 4 pins - MISO, MOSI, SCK and CE. However the on/off function has it's own pin - Pin 8.

It looks like on the main board pin 8 comes in on page 19, but goes straight off again to the power supply page. I think that's page 8, and comes in on the bottom left corner. Couple of transistors there (V2054 and V2051), and what looks like a thermistor (R2051). That's where I'd start poking about.

10

General Discussion Area / Re: car stereo question

« on: 08 December 2025, 09:51:09 »

I have the circuits for the radio (SQR88?) and CD player (CDP09?) used in the LC - Both Blaupunkt blue dot. What model number radio are you having problems with? I might be able to get the circuits and have a look.

Mark is correct about the de-bounce circuit - but is depends on the actual fault. Are you saying when you press the on/off button it sometimes works, sometimes doesn't? Or are you saying that the radio randomly switches on some time (seconds/minuites?) after you have pressed the on button? 

11

General Discussion Area / Re: car stereo question

« on: 07 December 2025, 23:01:16 »

Lots of generalisations, but...

The switch is usually connected directly to a microprocessor (uP). The uP is powered all the time, even when the radio is off. There are usually several operating modes, including a sleep mode where the power consumed is minimised. Pressing the switch generates an interrupt which 'wakes' the uP up from sleep mode, and it then turns power on (or off) to the rest of the circuitry.

The uP doesn't actually switch the power - that is done by a separate power regulator/control chip. The uP simply asks the regulator to turn on or off. Older designs will be a simple 'on/off' wire from the uP to the regulator. Newer designs may have a digital comunicaiton bus between the two.

So, if it were me, I'd make sure the on/off switch is working correctly, and the on/off signal is getting to the uP. Not much you can do about the uP itself, but if you can find an online circuit diagram for your radio you might be able to find the connection from the uP to the power regulator. The regulator will be quite a large device usually bolted to the metal chassis of the radio. They dissipate a lot of power so get hot. You can sometimes read the part number off them and locate replacements. 

Having said all that, if the radio is intermittent then chances are the uP and Regulator are Ok - silicon stuff is pretty reliable and unlikely to misbehave if correctly connected. It'll likely be a switch, crystal, resistor or capacitor playing up.

12

General Discussion Area / Re: Ukraine peace stalemate

« on: 05 December 2025, 10:59:15 »

People need to make up their minds - do you want an EU army/navy/airforce or not?

At the moment defence is not an EU function. Every European country (EU or not) has sovereign control of it's own forces. So whilst the EU is guilty of many things, it's got no role in military support for Ukr using any countries existing assets. Sure - it can provide funding for Ukr to buy stuff, but it has no control of any army, navy or airforce to send in.

If there were a "coalition of the willing" then one, some or all of the European nations could send in their army, navy and/or airforce now, with no approval required from anyone. That would certainly upset both the US and Russia, and would likely result in a response from Russia against those countries that took part. And worse, if Russia were to attack a NATO country as a result of their participation, that would not automatically invoke Article 5 of the NATO treaty, since it can be argued that the NATO country 'started it'.

I've said it from the beginning, this war is going to go on for 5+ years. The west will not get directly involved, and the best that can be hoped for is that western countries use that 5+ year period to re-arm. That's exactly what Poland, Sweden and Finland are doing, and to a lesser extent France and Germany. However, the UK response so far has been very poor. Lots of talk about 3.5% and 5% defence spending, but no sign of it actually happening.

13

General Discussion Area / Re: Budget.

« on: 01 December 2025, 14:32:44 »

Another one I heard from Martin Lewis yesterday evening, pensioners will not have to pay income tax on their state pension, even if/when the pension exceeds the 20% tax threshold, which it will do in 2027.
However, they will have to pay tax on their occupational pension.

Penson income has always been subject to tax, it's just that the SP has always been less than your personal allowance, so the applicable tax rate is 0%. The SP is always payed as the first tranche of your income.

What happens at the moment is the amount of your SP is deducted from your personal allowance. So if your SP is (say) £10K, and the 'normal' personal allowance is £12570, then your tax code will be 257 (12570 - 10000 = 2570), rather than 1257. This means any other income provider (work, occupation pension or private pension) will pay the first £2570 tax free, and then deduct 20% on everything above that.

If/when the SP exceeds £12570 it makes no sense for the govt to pay it all out, and then HMRC try to claim it back in tax. It would get really messy for pensioners whose only source of income is their SP. They'd end up filling in self assesement tax returns every year.

There must be some people whose SP already exceeds their PA. Anyone on the pre 2016 system with significant S2P/SERPS could be receiving close to £16K. I wonder how that is treated at the moment?

Hence my tax code changing from 12???M to 38M 

Yes, and if your SP exceeds your PA, then your tax code goes negative. This means that your other income providers end up deducting the tax you should have paid on the SP from the money they pay you. Works all fine and dandy, providing you have some other income from other sources from which the tax can be deducted.

However, if your only income is your SP, then there ain't no other source that the tax can be deducted from. It's a corner case at the moment because there can't be too many people who have built up sufficient SERPS/S2P to exceed the 12750 PA, but have no other retirement income. To have that much SERPS/S2P you would have to have been earning a good wedge when working, so it would have been foolhardy to not make other additional retirement provisions in addition to your expected SP.

However, if/once the old SP exceeds the PA that will change. Rachel from accounts seems to be saying the SP won't be liable to income tax, but does that mean those who are already above the PA threshold will get similar tax relief on their SP? That's what RonnyD is asking too. I can see this becoming a mess. 

14

General Discussion Area / Re: Budget.

« on: 30 November 2025, 17:27:00 »

Another one I heard from Martin Lewis yesterday evening, pensioners will not have to pay income tax on their state pension, even if/when the pension exceeds the 20% tax threshold, which it will do in 2027.
However, they will have to pay tax on their occupational pension.

Penson income has always been subject to tax, it's just that the SP has always been less than your personal allowance, so the applicable tax rate is 0%. The SP is always payed as the first tranche of your income.

What happens at the moment is the amount of your SP is deducted from your personal allowance. So if your SP is (say) £10K, and the 'normal' personal allowance is £12570, then your tax code will be 257 (12570 - 10000 = 2570), rather than 1257. This means any other income provider (work, occupation pension or private pension) will pay the first £2570 tax free, and then deduct 20% on everything above that.

If/when the SP exceeds £12570 it makes no sense for the govt to pay it all out, and then HMRC try to claim it back in tax. It would get really messy for pensioners whose only source of income is their SP. They'd end up filling in self assesement tax returns every year.

There must be some people whose SP already exceeds their PA. Anyone on the pre 2016 system with significant S2P/SERPS could be receiving close to £16K. I wonder how that is treated at the moment?

15

General Discussion Area / Re: Budget.

« on: 28 November 2025, 09:34:58 »

The reason that the £20K cash limit has been kept for over 65's is that SS ISAs are basically stock market investments, and these sort of investments are only suited to medium and long term savings. Whilst the returns on the stock markets exceed cash long term, they are volatile and can go up and down lots in the short term - 20% drops aren't unknown. Therefore, SS ISAS aren't really suitable for coffin dodgers who may need to cash in the investments at short notice.

Personally I think even £12K p/a is far too much in cash regardless of age.