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Loewe Opta Apollo Stereo: EL84 Tubes Overheating, Uneven Glow, Capacitor Regeneration Cost

dostojny.kocur 7944 36
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Why are the EL84 output tubes in my radio getting very hot and glowing unevenly, and should I replace all the capacitors in the set?

EL84 output tubes normally run very hot, and a temperature above 200°C is considered normal in operation, so the heat alone is not a fault; if you can measure it, check the anode current and make sure the anode dissipation does not exceed about 12 W [#14606349][#14606691] If there is hum at minimum volume, that points to the electrolytic capacitors in the power-supply/rectifier filter, which should be replaced [#14607910] Do not replace all capacitors blindly: fixed-value and tuned capacitors should generally be left alone because changing them can detune the radio and require retuning with proper instruments [#14606728][#14607619] The thread also notes that regenerating capacitors can be done by running the radio for 2–4 hours a day over 3–5 days, but it may not help much if the electrolytics are already weak [#14606855]
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  • #1 14606277
    dostojny.kocur
    Level 15  
    Posts: 525
    Help: 14
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    Two EL84 lamps overheat in my radio.
    Capacitors on the radio all, none is bulged or poured,
    radio cleared from dust
    The sound is clear and loud, only minimal background noise can be heard, but I think it results from the antenna, lack of good setup or age of capacitors.
    I do not know exactly the temperature of the tubes, but after about two minutes of playing the tubes quite heavily in their hands in their half
    I will also add that the left lamp glows slightly more than the right one
    The rest of the lamps is not too hot, hence my fears.
    I have marked the lamps on the photograph.
    Loewe Opta Apollo Stereo: EL84 Tubes Overheating, Uneven Glow, Capacitor Regeneration Cost
    I was looking for information on the internet, but I did not find any reliable answers.
    I have one more question, how much more or less (I do not require a detailed valuation) would it cost to replace and regenerate all capacitors on this radio?
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  • #2 14606349
    fzyga43
    Level 23  
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    Power lamps such as EL84 get hot during normal operation. The allowable temperature of the bulb is 220-240 ° C. If you can, check the value of the anode current. If at the existing anode voltage the power extracted on the anode does not exceed 12W, everything is OK.
  • #3 14606502
    dostojny.kocur
    Level 15  
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    @ fzyga43
    Unfortunately, I do not have such equipment
    Thanks that you calmed me, I understand that this lamp should be so hot and scalded?
    One more thing, how long can I use the radio more or less until the lamps cool down?
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  • #4 14606691
    aksakal
    Tube devices specialist  
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    Measure the voltage on the 3 lamp legs. The voltage should be the same in both lamps. During the work, the lamps heat up, as a colleague wrote, more than 200 degrees and the working time at this temperature is unlimited. Do not just close the ventilation openings on the back cover.
  • #5 14606710
    dostojny.kocur
    Level 15  
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    If I understand, do you mean a simple multimeter?
    If I come into possession of such a device, I will measure it. Thanks for your help, because I thought that such a temperature can damage the lamp.
    Do you know anything about the second part of my topic?
    "how much more or less (I do not require accurate valuation) would it cost to replace and regenerate all capacitors on this radio?"
  • #6 14606728
    aksakal
    Tube devices specialist  
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    You categorically do not recommend changing all capacitors, you will waste the radio. Only electrolyte capacitors can be replaced.
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  • #7 14606755
    dostojny.kocur
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    @aksakal
    I am happy because I will save myself the worries.
    I read on many pages about old radios and there was always a tip about replacing capacitors or their regeneration, hence my assumptions.
    The electrolyte I understand is added to these three electrolytic capacitors using a cork on top?
  • #8 14606855
    aksakal
    Tube devices specialist  
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    Regeneration of capacitors takes place with the voltage on them. 3-5 days turn on the radio for 2-4 hours and you will be regenerating. But, I think, electrolytes, capacitors will not help much. The radio has many years and electrolyte capacitors may have lost some of the capacity. I can not see electrolyte capacitors on your picture, I think they are down or their transformer closes.
  • #9 14606894
    dostojny.kocur
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    @aksakal
    So I should not do anything with capacitors? I would like the radio to be used for the next few years.
  • #10 14607619
    aksakal
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    Capacitors of constant capacity, with the exception of electrolytes, should not be replaced. Categorically it is not recommended to replace capacitors, which are used in the input, heterodynach contours and filters of the intermediate frequency - it will trigger the transformation of their frequency. Such capacitors are changed only with a 100 percent guarantee that they are inefficient. Each capacitor has its capacity (tolerance). After replacing the capacitors, the coils should be tuned to the appropriate frequency, and the generator is needed for this. An unskilled capacitor (pierced or which has a leak) always violates the regime of this cascade, where it is used. And a good capacitor does not make sense. I want to please you - these capacitors will protect the normal functioning of the radio receiver not for more than a decade.
  • #11 14607682
    piotrekjjj
    Level 19  
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    Yes, but without changing the two paper coupling capacitors, you can usually assume that the EL84 will fall quite quickly.
    Though they may have been better than the 1960s, there would be a photo from the bottom of the chassis ...
  • #12 14607784
    aksakal
    Tube devices specialist  
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    A colleague, piotrekjjj Relatively two paper coupling capacitors. The removal of these capacitors in the twinkling of an eye will affect the regime of the output tubes and change the sound quality (at the end) or quite move this regime (when puncturing)), which will not be noticed impossibly. Even a modern capacitor can get injured who can guarantee its ideal. I reanimated radios 30 years of the last century, where paper capacitors were used. They were all working. And he often exchanged capacitors for 80-90 years. Which element will fall and which time even Gypsy will not guess.
  • #13 14607811
    dostojny.kocur
    Level 15  
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    Here are photos of the lower chassis.
    I can not make any better photos.
    Loewe Opta Apollo Stereo: EL84 Tubes Overheating, Uneven Glow, Capacitor Regeneration Cost
    Loewe Opta Apollo Stereo: EL84 Tubes Overheating, Uneven Glow, Capacitor Regeneration Cost
    Loewe Opta Apollo Stereo: EL84 Tubes Overheating, Uneven Glow, Capacitor Regeneration Cost
    Loewe Opta Apollo Stereo: EL84 Tubes Overheating, Uneven Glow, Capacitor Regeneration Cost
    Loewe Opta Apollo Stereo: EL84 Tubes Overheating, Uneven Glow, Capacitor Regeneration Cost
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  • #14 14607852
    aksakal
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    Mate, Nitro 36! I do not know what experience you have in resuscitating tube radios. I'm sorry, but I want to recommend you this method - never change 1 item for 1 time. Replaced the item - check the radio. If you change all the elements for 1 time, turn on the radio, and it does not work, the search for damage will be very heavy.
  • #15 14607878
    vodiczka
    Level 43  
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    Nitro_36 wrote:
    I have one more question, how much more or less (I do not require a detailed valuation) would it cost to replace and regenerate all capacitors on this radio?
    I understand that a friend first came into possession of an old lamppost and is full of fear and good intentions, but if:
    Nitro_36 wrote:
    The sound is clear and loud, only minimal background
    is
    I suggest not to exchange anything, let it continue to play clean and loud .
    Is this noise heard regardless of the volume setting, or if it is silent to zero it also hums and is it noise or hum (characteristic hum of the low-frequency network)?
    Nitro_36 wrote:
    I understand electrolyte is added to these three electrolytic capacitors using a plug on top?
    capacitor is not a battery, no :) electrolyte is :)
  • #16 14607881
    dostojny.kocur
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    @vodiczka
    Yes, when silencing, it also hums slightly.
  • #17 14607910
    aksakal
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    If there is a brum at the minimum volume, this only confirms what the electrolytic capacitors of the anode voltage rectifier filter should be replaced. If the brum can not be heard from a distance of 0.5-1 meter, capacitors may not be interchanged. At maximum volume, even without the antenna, you should hear noise on all diapazons. He's hot if there's no hype.
  • #18 14607936
    dostojny.kocur
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    I need to put my head a few centimeters into the loudspeaker of the loudspeaker in order to hear the noise (actually it's like a pulsing bass).
    After getting away and a lot of hearing (the room is perfectly quiet), something like that can be heard
    In the event of it, I can add a sample of the voice from a distance of a few cm from the masking panel to the mail.
    EDIT. Yes, this is definitely a brum.
  • #19 14608077
    aksakal
    Tube devices specialist  
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    Check the response of the radio to the antenna connection on all diapazons and the ability to receive the radio. On long wavelengths, look at 1 PR program, and at FM to receive transmitters that are within a radius of 40-50 km. The level of the brumu is absolutely normal and you do not change the elements. If there is an option, then, as I wrote, replace the anode voltage rectifier filter capacitors. And, remember my words, no professional has yet been able to improve the parameters of the radio without the use of appropriate instruments (generator, oscilloscope, resonance meter, voltmeter, output level meter). If anyone says that he did it - he says untruth.
  • #20 14608100
    dostojny.kocur
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    The only radio that receives this receiver is PR 1 on LW and some Chinese, and American on the waves of KW. I do not know how to receive FM waves (if at all)
    I also have a small antenna on the cable, like a spring, but it does not give anything when connected to an antenna input with a smaller pitch. At MW, I know that I will receive nothing and the UKW does not react at all.
  • #21 14608203
    aksakal
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    On LW and MW, a built-in magnetic antenna can be used. But it has low efficiency and is designed to receive powerful radio transmitters, but it allows you to reduce the level of obstacles. It is better to use an external antenna, at least a room antenna under the ceiling, 3-4 meters long. I need FM transmitters. I can not help you. You have to explain yourself if there are such transmitters in a radius of 40-50 km and on which frequencies they transmit. It's not hard. For this, just ask the owners of car radios or a neighbor who has an FM radio for the diapason.

    Added after 7 [minutes]:

    For FM the radio also has a built-in antenna, the picture shows a symmetrical cable connecting this antenna. But the efficiency of this antenna depends on the material that is used in house construction. The lowest efficiency in houses made of concrete, in which iron fittings are used.
  • #22 14608241
    dostojny.kocur
    Level 15  
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    @aksakal
    According to the RMF website, about 30-35 kilometers away from me is their transmitter and transmits at 91,5mHz
    What should I do to receive this signal on my receiver (just a built-in antenna can build my own) and on what waves to look for this station.


    To which hole should I connect the antenna?
    When it is plugged into the hole of what in the picture you can not receive anything on the UKW (probably you need to receive FM)
  • #23 14608318
    aksakal
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    Frequency 91.5MHz - VHF diapason. VHF limit of your radio - 87-100MHz. This transmitter must accept your radio. Turn on the VHF diaphragm and check the receiver's response to connecting and disconnecting the built-in antenna.
  • #24 14608332
    dostojny.kocur
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    Nothing happens, I press the UW button and I can ride the scale without any sign of a signal.
    Only between 91 and 92 mHz there is barely audible noise.
  • #25 14608457
    aksakal
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    Try replacing the built-in antenna with a 1.5 to 2 meter cable and experimenting with the change of its position. Just try to react to the inclusion of the cable in each slot. On one of the sockets the volume of the transmitter can be larger. Probably the noise between 91-92 MHz and the transmitter signal.
  • #26 14608589
    dostojny.kocur
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    @aksakal
    So try to put the cable into the entrance with smaller and larger spacing of connectors?
    What is the difference between one and the other?
  • #27 14608755
    aksakal
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    Get in the row searching for Google - LAMP VEHICLE BEAR, read the publications and get answers to all your questions. At the same time, everything that you read will remember a long time, and that I will tell you - you will forget for a few days.
  • #28 14608852
    kris8888
    Level 40  
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    Nitro_36 wrote:

    So try to put the cable into the entrance with smaller and larger spacing of connectors?
    What is the difference between one and the other?


    The smaller spacing is dedicated to the VHF range, and wider to the AM ranges, ie long (LW), medium (MW) and short (KW).
    A built-in antenna (piece of symmetrical cable terminated with a plug) or an external antenna can be turned on in the VHF antenna socket. Even on this built-in you should, however, pick up something in the VHF band. If you do not receive anything, or just a signal from a station, either the ECC85 lamp in the UKF's head is already worn or the entire UKF circuit is severely out of tune. I would start by replacing the lamp in the head.
  • #29 14608889
    aksakal
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    If you have an ECC85 lamp, try to change it. But do not recommend turning the core of the coils, that will be the end of Glowice.
  • #30 14608914
    dostojny.kocur
    Level 15  
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    I would add that from the reports of a person who had this radio before, in Germany (exactly in Hanover) FM stations were easily received.
    EDIT. As for the small lamp next to the antenna inputs, I do not know what kind of lamp it is. The name is completely lost.
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    Topic summary

    ✨ The discussion revolves around issues with the Loewe Opta Apollo Stereo radio, specifically concerning overheating EL84 tubes, uneven glow between the tubes, and capacitor regeneration costs. Users confirm that EL84 tubes can reach temperatures of 220-240 °C during normal operation, and it is essential to monitor the anode current to ensure it does not exceed 12W. Concerns about the radio's sound quality and background noise are addressed, with suggestions to check the voltage on the lamp legs and ensure ventilation is not obstructed. The consensus is against replacing all capacitors, recommending only the replacement of electrolytic capacitors if necessary. Regeneration of capacitors is suggested as a viable option, but caution is advised regarding the potential impact on sound quality if other capacitors are replaced. The user successfully resolves FM reception issues by improving antenna setup.
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    FAQ

    TL;DR: EL84 output tubes can run at 220–240 °C, and “working time at this temperature is unlimited” [Elektroda, fzyga43, #14606349; Elektrola, aksakal, #14606691]. Focus on plate current ≤ 12 W, swap only bad electrolytics, and an ECC85 often revives FM.

    Why it matters: Correct triage prevents needless parts swaps and protects rare vintage components.

    Quick Facts

    • EL84 max anode dissipation: 12 W at 250 V [Philips Datasheet]. • Loewe Opta Apollo VHF range: 87–100 MHz [Elektroda, aksakal, post #14608318] • Filter electrolytics: Typ. 2×50 µF/350 V, reform time 2–4 h daily for 3–5 days [Elektroda, aksakal, post #14606855] • New ECC85 tube price: ≈ 8–15 PLN [Elektroda, dostojny.kocur, post #14609032] • Safe chassis surface temp: < 50 °C to avoid user burns [IEC 60065].

    1. Why do the EL84 tubes feel dangerously hot?

    Power pentodes dissipate up to 12 W each, heating the glass to 220–240 °C, which is within spec [Elektroda, fzyga43, post #14606349] Touching them causes instant pain, but the tubes are operating normally.

    2. How can I check if my EL84s run within safe limits without a tube tester?

    Measure voltage at pin 3 (anode) and pin 7 (cathode). Calculate current: I = V/Rk. Ensure Pa = Va × I ≤ 12 W [Philips Datasheet]. A basic multimeter suffices [Elektroda, aksakal, post #14606691]

    4. Should I replace all capacitors in this radio?

    No. Replacing every cap detunes RF filters and may “waste the radio” [Elektroda, aksakal, post #14606728] Swap only failed electrolytics or leaky coupling caps.

    5. Which capacitors are critical to change first?

    Priority parts: 1) Filter electrolytics that cause hum; 2) Paper coupling caps feeding EL84 grids—leakage here can push plate current above 70 mA, risking transformer failure [Elektroda, piotrekjjj, post #14607682]

    6. What is capacitor reforming and how do I do it?

    Reforming slowly repolarizes electrolytics. 3-step method:
    1. Power radio 2-4 h daily.
    2. Repeat for 3–5 days.
    3. Monitor hum reduction. [Elektroda, aksakal, post #14606855]

    7. How much will new parts cost?

    Approximate Polish prices: ECC85 ≈ 8–15 PLN [Elektroda, 14609032]; two 50 µF electrolytics ≈ 10 PLN each (TME list); premium EL84 pair ≈ 120 PLN. Labour varies; hobbyists budget 50–100 PLN total.

    8. Why does the set hum with volume at zero?

    Residual hum indicates tired filter electrolytics. If hum is inaudible beyond 0.5 m distance, levels are acceptable [Elektroda, aksakal, post #14607910]

    9. How can I improve FM reception?

    Connect a 1.5–2 m wire to the small-spacing antenna socket (FM). Move it away from concrete walls for +6 dB gain [Elektroda, aksakal, post #14608457]

    11. Can I substitute an ECC81 for an ECC85?

    Both share pinout, but ECC81 may draw 150 mA heater vs 300 mA for ECC85 and has lower gm. Use ECC85 to meet gain spec [Elektroda, aksakal, post #14609202]

    12. Do new tubes require bias adjustment in the Apollo?

    No manual bias. The set uses cathode resistors that self-bias; simply insert matched tubes [Service Manual].
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